So quick update; Managed to get the bike together. It fits pretty well for me aside from the shockingly short 250mm seatpost. Thankfully after some sleepless nights scouring AliExpress and other local Online stores (namely Lazada and Shopee here in SEA), I've managed to find a longer seatpost. I've also found the seatpost on AliExpress, and I'll update the original post with some links.
Basically, just transferred the parts I had on my "Gravel" bike onto this one. I'm trying to save up for a hydraulic groupset so the Ltwoo R3 would do fine for now. Tires atm are Continental Ultra Sport III 28c. I'm planning on going for 32c in the future for a bit more comfort. I'm planning on getting a longer stem as well so i wouldn't be finishing the build anytime soon.
I'll wait for the new seatpost and stem to arrive before doing the final setup.
Those aero/D-shape seatposts sadly are all a pain in the ass to replace. Almost all of them are proprietary and you can only use the one that came with the frame or replacements directly from the frame's manufacturer.
I wish you luck though finding one. If this is a re-brand from another frame, you might be lucky but usually it's a dead end :/
Thankfully I managed to find one after scouring around AliExpress. I'll post the links on the original post when I can