I'm not an expert on the BEL genetics, so someone can correct me if I'm inaccurate. From what I know, all the lines of BEL (Mojave, Lesser, Butter, etc) are compatible. It's more personal preference and what fits into your projects, if you want pure white BEL then work with Lesser or Butter (some may have bug eyes), if you like the grey head and yellowish/off white BEL then super Mojaves are the way to go.
To answer your second question, yes if both parents are BELs then you would produce all BELs. Example: Super Mojave x Super Mojave= Super mojaves, or Super Lesser x Super Butter= Butter Lesser BELs
Hope that information helps!