Ah yes, the Alugear ripoff. I have the same but from Ryet, which were quite a bit more expensive. But they look amazing and shifting is great. Might give these a go next time.

Do the Ryet ones bought as a set come with the aero cover or do you have to buy that piece additionally?

On my XMCS wheelset with 26mm IW, my Hutchinson Caracals in 700x40 are 44mm at their widest and 39.5mm in height.

The new Conti GP5000 S TR (NOT the ghetto-ized all seasons) seems to be out, shipping, and in stock here https://r2-bike.com/CONTINENTAL-Tire-Grand-Prix-5000-S-TR-Tubeless-28-700-x-35C-BlackChili-VectranBreaker.
Havent seen a rolling resistance test yet, but i suspect that it's as fast as the 32, that was as fast as the 28, give or take.
With a wide ass rim, the existence of this tyre just reset the gold standard for fast road bikes for most people, as far as i'm concerned. If you're 80kg, you've got no business being on 28C when you could be on wider tyres. I have 32 measuring 34mm at the back, i'm never going narrower again, and i'd love to test this 35 to see how it feels. The less is worry (punctures) and feel (vibration / comfort) potholes and bad asphalt, the better. Especially in the mountains, especially in spring / autumn when alpine / forest roads can be greasy, dirty, mossy, wet, gravely, and so on. I dont like that they don't have a tube version though, but i also dont think China is selling 35C TPU tubes, so maybe it's got to be tubeless.
And so, that frame looks very interesting.

Try the 38c Schwalbe slicks-real width is right at 40mm on 26 IW rims.   Dive bombing inside lines on asphalt is hilarious fun.

https://www.bicyclerollingresistance.com/cx-gravel-reviews/schwalbe-pro-one-tle-38

They are made in different factories, by different people, with different QC processes. Remember, too, that EN standard compliance is a baseline for legality in China, but you need ISO4210 or an extended version of that standard for compliance and liability reasons when selling outside of China. There are some Aliexpress brands that seem to share factories with clone makers, so there is some overlap there; but for the "higher end" brands you mentioned, their only likely commonality is that they are in China.

This is like asking what the difference is broadly between a burger at McDonald's and the bar down the street. Both are made close to you and they pass local health inspections (hopefully). That's about it.

The companies and engineering staff behind each of the frames are totally different as well. Their approach to development is also really different. This is a bit of hearsay, but its a good example: when LTK / Permeants wanted to clone the Giant TCR Advanced SL. They put that bike on a deflection rig and then designed from the ground up form and a layup that replicate the ride feel and quality of the Giant by cloning its deflection numbers, not its shape. We see similar indications of benchmarking and then ground-up design from Elilee and Seka as well.

As a theoretical exercise, it would be interesting to put an '80s vintage Vitus 979 (stiff enough for Sean Kelly to win many sprints, and a lot of NOS frames in circulation) in a deflection rig and duplicate its headtube and BB stiffness stats in carbon fiber just to see how light you could go, and then start extrapolating iterations at +50 gram material increments for stiffness and life cycles to destruction.

Definitely.

Hopefully 1 1/8" steerer diameter; 1 1/4" shimmed to 1 1/8" is very much sub-optimal.

Made in Italy steel for 2500 Euro is a pretty good turn key value proposition.

https://bikerumor.com/battaglin-milano-teases-affordable-made-in-italy-steel-gravel-bike-only-2500e-complete/

The brand's last name is Dud-why resellers don't use Reddit abuse to pre-check brand names for Western markets is so puzzling.

You can also go fancy and get one of these: https://www.aliexpress.com/item/1005007592915101.html

I'm in the process of making a front wheel stand with a nice piece of oak. It will rest on a wobble cushion

Yeah, that would the easy mode and probably doable with paired 2 x 4s cut to length.