One likely cannot make too many generalizations other than the top NAIA programs including Lewis Clark, Oklahoma City and the like are stronger than the better DIII programs.
Scholarships and academics make a distinct difference.
When you are out of the top NAIA programs, things will even out quickly. There are many NAIA programs who travel to TX and play the top DIII programs there.
Most of the games are not too competitive. The DIII programs are stronger, much stronger in some cases.
In Southern CA, Chapman plays a schedule which often includes NAIA programs and they are quite competitive with better teams from that area.