Well, they sell it with a ZTTO Z12 chain, so you won't need a flat top chain judging by that...

So would ot be fair to assume that it also works with standard Shimano/YBN/KMC road chains? If so, that would be a big advantage over Sram cassette.

Also, question to Aliexpress gurus: are there any Kocevlo integrated handlebars with -6° stem and 75mm reach that would be a ailable in 380/110?

The only bar that seems to fit is the Alanera copy (available without fake logos), Rpantahi is close, but specs are confusing (specs printed on the bar indicate 75mm reach 125 drop, specs in the description indicate 77mm reach and 127mm drop and the identical Kocevlo bars are -10°).

Ltwoo electric gravel groupset does look very interesting, as long as it works with Sram's 10-44t cassette.

You can get the same frame as Hygge directly from manufacturer (Winow). It's not the lightest frame around, but it should do the trick. Geometry itself is fine, although it does have relatively slack headtube angle, similar to Colnago and BMC. IMO, Winow is at least on par with TanTan, if not better,  considering it is OEM for other brands (i.e. Winow is OEM of Falath Pro)

On the aggressive side there's also SPCycle 053D that accepts 32c tyres. Velobuild VBR177 is a good frame too, quality is higher than their other frames like 168 because of EPS technology.

On the more relaxed side, Elves Eglath would be a nice option. Yishun 068D is nice as well, but you'd have to paint the frame yourself

Thinking about Fovno Aurora cranks too. To my understanding, the crank arms should be compatible with this power meter spider https://xcadey.eu/xpower-s-sram-3-bolt-110bcd and 110 BCD 5 arm Garbaruk 1x chainring?

Depends on the crankset. The Racework carbon crankset is about 377g and the Goldix/Zeroing crankset w/hollowed out crank arms is about 475-480g. In order to match those weights, you have to go Dura Ace of SRAM Red at a significantly higher cost.

I did some digging, found weight for non-Shimano spindles - 160g for steel, 90mm for alloy. 70 grams savings is less than  0.1% of total system weight (typical accuracy of digital scales is 0.1%). Comprimising the durability of one of the highest stress areas for literally meaningless gains is not what I'd recommend.

I have 24mm 7075 alloy axle spindles on all my bikes. I haven't had any issues...yet. The weight savings are very noticeable. All I do is hill climb and go out of saddle quite often. Though I weigh between 68-70kg. I figure at my size, I can get away with a lot of weight weenie hacks that thicc cyclists wouldn't be able to pull off.

What's the realistic weight difference between 24mm steel and alloy spindles? 30, 50, 70 grams? 100 grams?

Does anyone know what is the chain compatibility of chinese XDR cassetes? Flat top Sram chains or regular Shimano spec chains?

https://a.aliexpress.com/_mKoZuCA