It does count so to say OSU played a weaker schedule than N. Illinois is silly.
Besides N. Illinois isn’t an AQ.
If OSU loses, should Northern Illinois play in the title game?
Doesn't matter. A non-AQ team ranked in the top 12 (or 16 if it finishes ahead of an AQ team) is guaranteed a BCS game. If NIU is undefeated, should it be in the national title game?