Hi, I did the Asaatthi subraces... I don't know how it appears in the book, but the intent was to provide tweaks from the standard. That is, assume 3 racial hit dice. Apologies for lacking feats and skills, but again, assume the standard. There were some tight space constraints, so I tried to be as economical as possible. CR shouldn't be tremendously different, though I'd adjust the misbred CR modifier to race +1 (I had set it as +3, which is silly), and a CR of 2 for the Lowest ones.
My estimation was that similar spellcasting levels stack. That is, normal Asaatthi + 5 wizard levels casts as an 8th level wizard, though only has 1 bonus feat and 5 levels toward a familiar.