My 5 cents as someone who's building several velobuild bikes atm, have ordered 6 carbon wheelsets over the years, have been using aliexpress carbon handlebars for years, weighs c.80kg, have never ridden gravel, sucks at MTB, and essentially only does road cycling:
Velobuild GF003 (it's very finished and looks super sturdy)
Sensah or Ltwo 1x (for your weight & steep stuff i think a 1x with the biggest cassette you can fit is best. It's very easy to run out of gears on a 2x setup)
I have had good experience with Farsports wheels, if you contact them directly by email you can configure a lower priced option than what they advertise (get Sapim spokes, the rest, afaik, doesnt matter too much. Get wide gravel rims). Buy from whomever though.
Spend money on good tyres, that correspond to the type of riding you will do most.
Steep + heavy = hydraulic, most probably? My builds are mechanical with Jagwire KEB-SL housing, but i havent riddem them yet so i can't speak of breaking performance. Although if you use mechanical + Jagwire KEB-SL brake housing + don't route everything internally (maybe route the front brake externally around the handlebars then into the frame to limit awkward angles) + 160 rotors (or more?), you're probably going to get a bike that brakes very well.

Budget wise, you should be below 2k. Not sure if you can get to 1.5k. Maybe 1.5k + shipping?

Now i may sing a different tune after i've ridden these VB frames, but so far, handling them, they look solid. You're heavy but i think we'd hear more horror stories if carbon frames kept breaking like matches. I have friends who ride mountain bikes like pro riders, i would not recommend them anything unbranded because i know they push equipment to the limits & racers should race race cars. Meanwhile, you're "just" heavy. If you hit a big ass pothole, you're more at risk of breaking your gear, but idk if this risk is materially higher using a velobuild frame and good wheels. If you pick aluminium wheels, the bike wont feel as nice, but they will be somewhat bulletproof and much cheaper. Something you could upgrade later on maybe depending on feel?

Happy riding!

My 5 cents from someone who's bought 7 carbon wheel sets: get Sapim spokes (ideally, Xray) over Pillar. They cost a bit more but if you plan to actually use the bike, the difference is meant to be worth it. Better ride quality, lighter, less prone to mechanical failure.
The hubs probably matter less. Ceramic bearings are utterly unnecessary. I've had novatec hubs forever, they just work. You don't want hubs that need constant maintenance.

Has anyone else had issues with water ingress? I'd like to drill a hole in the bottom of the BB shell, but this seems like a perfect way to start a crack.

My unqualified opinion says: don't worry too much about causing a crack when drilling. Be careful, take your time, but you're not going to cause your frame to crack by drilling a small hole or 2 in the BB area.

I find my interest in AliExpress parts has started to wane. I do like the carbon components, but other than that I still would rather stick with name brand drivetrain parts even if I have to wait for discount sales or buy used domestically.

Same here. Prices have been going up a lot. Now they have to charge VAT to the EU, that didn't help, but on top of that, prices are often so high that you can spend virtually the same amount buying from a legit european online bike shop. Very disappointing. Aliexpress used to be cheap stuff that usually worked, sometimes didn't, but if it's not cheap anymore...

People vote with their feet, or with their money. I'm about to buy several VB frames.
Just like the future of twitter is some vetting system so that the irrelevant voices are drowned out, we would ideally get people's views weighted by the number of miles they've ridden, over how many years, the watts/kg they can do, and the bikes they've ridden. Just because you dont get medical advice from your hairdresser and vice versa.

Everybody wants a stiff yet comfortable frame, but who can actually tell the difference? How many times is the difference actually due to one bike fitting better, a different wheeslet, different tyres, different tyre pressure? Or pure subjectivity of the rider, like day 1 is sunny and you're fresh, day 2 it's cold and you're tired. Do you think your riding experience with the same bike will be the same?

I have a giant propel with farsports rims & sapim spokes. And a cannondale supersix himod with campag bora wheels. I can tell you i get wheel rub out of the saddle sometimes on the giant. I don't think i do on the cannondale, but i never ride them side by side on the same routes. And i wouldn't know which one is stiffer, and if it told you, that opinion would only be worth something if i had isolated all variables but the frame. I'd have to change the wheels, the bars, even the crankset. Needless to say, i'm never doing that. Is a frame that flexes actually flexes, or do you have the wrong bottom bracket, crank, bars, wheels, tyres, or pressure?

Then there's the question of "good enough". A given frame might be better, but if it costs double (or 8x more) and you can only tell the difference by riding 1 right after the other in a strict experiment, then most of the bike riding population should be perfectly happy with the cheaper one.

Then there's the question of status. People like to flex. I have friends who literally take pride from paying full retail price for stuff. For them paying top dollar with sticker shock is a badge of honour. With behaviours like that, you have the luxury industry, like Pinarello.

Anyway.

On relative value between brands you listed, Velobuild, as far as i can tell, sells quite a few more bikes than most competitors. Business wise, that could justify their lower price point. From YT & forum content, it is not clear to me that a dengfu or a carbonda is automatically better. And Winspace and Elves probably have better finish and QC, but if you get one of the VB that does NOT have problems, is it really a better bike in a way you can measure? If you get a poorly finished VB one, it seems that people get frustrated for a bit, then the problem gets fixed. I guess the more you pay the less you should expect to get your hands dirty. Some people like that, others don't.

It also seems clear to me that the VB177 is better made than the 168: it seems VB (or SPcycle, rather) is getting better over time.

Winspace is paying youtubers a lot, their marketing budget overall seems quite important. Someone has to pay for that. They're like Farsports, in a way, their pricing has gone up a LOT in recent years because they're marketing themselves, successfully, as a legit brand, not just an OEM.

Blablabla. Back to my starting point: voting with my money, I'm about to buy several VB frames. Maybe i'm mistaken, wish me luck

Thanks. Yes, admittedly, I'm not at all well versed on geometry and I did notice that the tubes seemed more geared towards weight savings in some and aero in others. 

I currently ride a 2011 S-works SL3 with R7000 105 components. Rim brake, obviously. It's on its way out and I'm not that happy about what you get for your money from the LBS these days, so want to build up my own bike. Not just for the cost savings, but also for the learning experience.  I thought I'd go with some frames that were similar to the SL7 but obviously I've missed the mark. I'm obviously many years older now, and I'm wondering if my reach has shortened a bit.  I'm also heavy enough that the weight savings from a very lightweight frame will be wasted on me. I'd rather go with a frame that is a bit heavier but well made and remains stiffer for longer.  I don't race apart from a couple of 160km sportive's per year, so happy to go with a more endurance type bike.

I know this is a very open-ended and question, but if you do have any suggestions about a frame that might be a good match, let me know. Thanks.

Will depend on where you live, but if you're happy with rim brakes, look at branded second hand bikes, you will get the most value out of those. If it comes with shitty wheels, get 60mm carbon ones, you can get a set shipped to you for c.600 usd, or also buy that second hand. Pay attention to the brake track though. Giant TCR, cannondale supersix, there are so many of those for sale and they're so good, you can't go wrong.

Good to know. I recently ordered ONIRII BR-05 calipers and from all appearances look like rebranded ZRace BR-005 calipers.

On Alibaba those are labelled IIIPro. https://www.alibaba.com/product-detail/LS-IIIPRO-Road-Bike-Brake-Calipers_1600550173826.html
I wonder who actually makes that stuff.

I dont remember seeing the usual suspects (velobuild and the likes) offering 130/140. But https://shop.fullspeedahead.com/en/stems/road-gravel/ns-acr-stem does offer 130/140; have you tried aliexpress? Worst case either you get an FSA one, or you botch something. Someone on the forum did a nice hack, routing outside the stem, it looked super clean, cutting one of the spacers for cables to enter the headset area. This means you can half legit run a regular stem and still route internally, I believe.