Transition from Spacer to stem looks a little bit weird? But Just my 2 Cents.
Anyway: i text via WhatsApp with Long Teng, to customize a the frame. What i have to Order due to Headset? Should i told them something specific? And Where i can buy later from Another company spacer, c-ringe, Headset, One Piece Cockpit, etc., that it fits to the frame/fork? And Where to Order Another thru axles? Budget for Headset, Handlebar and Axles Round about 400-500€.
FSA no55r (either standard or low stack version) headset or no69 (external cables). I used no69 as I have Zeno hydraulic couplers and this was easiest for me.
People agree not to use Long Teng headset. It's cheap and some say not good.
A good option for one piece handlebar (in my experience) but not on this bike is the Bigrock Skyline it has good size availability, cheap enough with codes on AliExpress, and is FSA ACR compatible. You might want to look at the Speeder and Light Carbon options as they are cheap enough and FSA compatible I think from what I have read.