There aren’t many DIY keyboard parts/shops in my european country (at least I couldn’t find one), but I found GMMK keyboard in a local (mostly online tho) shop. Is it a good pick? Will it allow me to freely rebuild it with other parts (even pcb)? How is it with software and features? Does it lack any featuers I may not know I may need (I never have used so small keyboard, my current one is TKL)?
the GMMK is a solid board, I have a fullsized V2, BUT newer versions dont support QMK and frankly I cant suggest any keyboard that cant be customized by QMK or controlled by VIA (gui for QMK).
Keychron is my go to safe quality prebuilt board. They have a wide selection of layouts, switches, caps and even bare-bones setups that come without caps/switches.
I would suggest seeing if you can order one from them over the GMMK just for QMK support alone.
https://www.keychron.com/
I personally drive a K4v2 which only has unofficial QMK support but at least it has some!