re: If Ohio State is #1 seed, who would give them a tougher match?

If you really want Ohio State to have the toughest semi if they're #1, you should root for Oklahoma to win and the committee to drop Clemson to #4 since Oklahoma will have 3 ranked wins and Clemson will have zero.

It would then be:
#1 OSU #4 Clemson in the Fiesta (to prevent Clemson home advantage in the Peach)
#2 LSU #3 Oklahoma in the Peach

although that means that LSU has to overcome the thing you said about OU's opponent's loses the final, which I don't think is really cast in stone, just like #1 or #3 never win isn't a rule either, although none has done it yet in 5 tries.