I don't know that the coaching staff specifically holds stuff back for a big opponent. However, there may be things that they see on film that they will game plan for so we may see things we haven't seen. For example, in 2016, I believe the coaching staff saw something about their FG block unit that made them think they could block one. You may recall that Allen said he almost blocked one earlier in the game and adjusted slightly to block the kick that turned into a TD.
I think if the defense and offense play as well as they can play, it will be a close game. That's obviously a big if. But I do think PSU is the best team OSU has played this year by a decent amount.
If it is a close game into the 4th quarter, it will be interesting to see how OSU responds. They have not had a close game this year and who knows how they will respond.