Looks really good. Great to see a low-poly modeller. WELCOME!
SFC 1 takes lods if you want but no light maps, textures are in *.bmp format, they do take break models.
SFC 2, OP are like SFC 1 but can take light maps, textures are in *.bmp format, they do take break models.
SFC 3 does NOT take lods, the hard points for heavy and primary weapons are reversed from previous versions, they take both light maps and damage textures, they do take break models. Texture maps can be in *.jpg, *.bmp, *.tga, and *.png. SFC 3 also takes several custom UI and glare files.
Scales are the same across the whole series. Think I read somewhere 20:1.
Feel free to ask questions, we are always excited to get an influx of fresh talent and ideas!