Sorry for not replying earlier. I was too busy mountain biking :-).
First of all, the bikes rides like a charm. It climbs so well and I also did hit jumps / drops of around 40cm, it feels very capable in that regard. The 120mm Sid with 35 stanchions feels like a perfect fit. I hear some minor rattle when I drop/jump, which i guess is the hydraulic brake hose in the chain stay. I used foam for the inner routing, but this was almost impossible to get into the chain stay.

Generally I am very very happy with bike. I need to cut down the carbon post by a few centimetres and get a quick release clamp for riding down nasty stuff.

My first training race is yet to come in April.

Regarding chainline:
I guess the 55mm is because this is a direct copy from a Scott scale (2023 model upwards), the 55mm chainline is used.
I didn't even try to use standard boost. I am 100 percent sure this is due to UDH being used by SRAM Transmission, which all use 55mm chainline (MTB wide standard). All transmission chainset use MTB wide / 55m.

What I did: I use a standard bb92 dub bottom bracket, and bought the spacer set from SRAM. I follow the SRAM dub manual using a 3mm spacer on the left and a 5mm spacer on the right side.
I use a SRAM X0 chainset with integrated power meter with 175mm / 32t.

You can get the gx transmission chainset for around 100 to 150 euro new now. I also like the style of the transmission, especially the x0 with the hole in it.
All transmission chainsets are compatible with standard eagle chain and derailleur. In my case the gx axs.

The chainline doesn't cause any issues, it shifts perfectly, no need to setup or change anything (beside b tension of course).
My rear wheel is standard boost obviously.

I don't have any pictures, but I might post some next week. I don't have the bike with me right now.

I am going to build mine with GX T-Type transmision with the old sram cranks for boost, but, with a 0 offset 34T, this will give me the 55mm chainline.

By the way, It's been more than two weeks since I ordered my frame form Aliexpress and SPCycles haven't send it. How long did it cost to send your frame? Yours was raw finish, mine will be metallic paint so it still goes slower

How the Zrace brakes perform? I bought the x2 model, they are very light. The same weight as XTR and with very good machinig

Ordered a frame in red last night. Hope they solved the BB issue. I will post pictures when it arrives