I've been running ZTTO 9-50 cassette for 2 years now.
No major complaints.
Sure it is not as refined as Shimano, or Sram, but it is extremely light and shifting is still reliable.

Is the Q factor of the SPD-SL version the same as on Look, or is it wider (like Assioma Duo-shi)?

Let's goooo!

Not everybody is using power meter for training.
You might use it just as a simple "power estimator", to help you control your efforts on longer rides.
+-5% or even +-10% is good enough for that kind of use. It is still much better than using just HR alone.
And why pay 500+$ for +-1% device, if you don't need that kind of accuracy?

I might buy it for my GFs bike. ¯\_(ツ)_/¯

After watching GP Lama's video, I did another test comparing the Xcadey to my Kickr.
What do you guys think?
The test procedure was as follows:
- Before starting, I calibrated the PM with my Garmin
- I competed in a Zwift race
- For comparison, the first 20 minutes, minutes 20 to 25 with two efforts
- After the race, a sprint 1
- Before sprint 2, I calibrated the PM again via the Garmin

What do you think of the data? Not as inconsistent as with GP Lama, but also not particularly accurate?

I would say yours if OK, no drifts after sprint consistant readings, but a bit high.
I observed the same on my unit, and also other users report that reported power values are always ~5% too high.
If you scale the power output to about 95% (in the Xcadey app) it gets really close to values reported by other power meters.
Not sure how can they get this wrong, are chinese watts different to western?
Or are they using a wrong calibration method in the factory?

Honestly not really acceptable for something that is advertised as 1% accurate.
But considering the price I can live with it.
On the other hand there are other units on the market for similar price that are more accurate.

Did anyone observe a difference in offset depending if you are in which front chain ring you aremin?

That is something I was wondering myself, but I use 1x so I can't test that.
Also it would be worth testing how much does chain alignment influence the values (ie. running on the big vs small sprocket).
But form what I was able to observe on my unit, there is hardly any difference.

Leese carbon crankset 165mm DUB, for ~$145 after coupons: https://www.aliexpress.com/item/1005008832402315.html
Elita one 3D printed saddle (Selle italia SLR copy), for ~$38 after coupons: https://www.aliexpress.com/item/1005007562893612.html
Carbon stem with spacers, for ~$44 after coupons: https://www.aliexpress.com/item/1005010070357991.html
Xcadey "random number generator" for ~250€: https://www.aliexpress.com/item/1005010254190071.html
Zrace DUB BB, I have several different models of these, and they are fine... ~$15: https://www.aliexpress.com/item/1005006290316561.html
Cheap chainrings ~$18: https://www.aliexpress.com/item/1005008343507378.html

Yes, it is the same shape/design, but operation is a bit different between mechanical and hydraulic brake versions.

In the hydraulic version you can shift multiple gears in one push in both directions.
But the mechanical brake version is different, the thumb lever only shifts one cog at the time.

I received R9 mechanical a few weeks ago, haven't mounted them on the bike yet...

But if it is the same style thumb shifter as Hydro R9/RX why could you not shift multiple gears at once as Alex Jones mentioned?