I'd like to point out that Penny will do vaginal both on the pure route (no corruption), corruption route and NTR route just fine. If anything, it's the anal scenes that won't happen when on the pure route.
Of course, it's generally also smart to discern between the corruption of the female character and the corruption of you as MC. This also actually influences things. Depending on your own corruption, certain things won't be options because they simply don't exist in your mind (purity).
I did a purity run without any corruption of either the MC or any of the girls and I was actually positively surprised that even when you do not pay Frisha's debt, she in fact does go to his room but does nothing with him. So she stays true to you, because she has no corruption. This was her not as a virgin however, she was in a relation with my MC.