Wondering the same. In my experience the Neco expanders are very long but actually pretty low quality.

I bought the frame in Ferrari Red and will get it delivered soon. [I also ordered a Yishun 1088 and 068 as well as a TanTan TT-x38).

I plan to build it with mechanical 105 12 speed, and I am hesitating with the wheels. (Either LC or Elitewheels).

I just got all my 4 race bike stolen in a single night, and I am waiting for the insurance to maybe refund me some part, so I am a bit cold on spending money now.

I'd be scared to run Ltwoo's electronic setup for gravel. You'd be screwed if you were riding in a remote area and your RD decides to stop shifting.

Is there any way just to get the 105 Di2 shifters, calipers and the FD/RD derailleur only? You can cut weight going with an Ultegra cassette/crankset or go with an aftermarket setup.

What 11 speed 11-32t cassette would you recommend with ER9? Nothing crazy like DA/Red, I was thinking about trying SLR2 sold by Lexon store or Sunshine

Serves them right for refusing to sell Shimano and SRAM components to the US.

it's usually a literal translation of some slogan that works in Chinese

Do you guys know a suitable handlebar which is 360 or 380mm wide?

LC has only an 400 wide option. With 370 shoulders not ideal.