Hi Bernt! Welcome to MWS ownership!!
All MWS have nigh on identical internal workings
Stock circa 300 FPS on 134a / upto 330 on Green
SixG Super Nub is great drop in range and accuracy upgrade
Longer barrel will increase FPS, but not increase accuracy
Floating valve alterations are needed to reliably and efficiently increase FPS
Dont get too hung up on FPS, these MWS guns punch well above their weight!
I dont see the need for more than 400 FPS on 0.2g, once you go higher youre increasing wear and efficency / consistency will suffer
As for GBB pistols, if you want performance to match the MWS then it has to be Hi Capa