You could say that Paul is basically a different person in each route — or at least not quite the same one. Depending on the player’s choices, the characters evolve, and their backstories shift along with them.
For example, the Mila from the loyal route is literally repulsed by the idea of cheating, while the Mila from the NTR and NTS routes sees it as something possible — even preferable at times.
Same goes for Paul. In the loyal route, he channels his frustration into the gym, and at some point, he just gets tired of holding back. That’s why he looks more jacked there. In other routes, he’s a bit less ripped.
Also, yeah, there are some style inconsistencies here and there — something I should probably fix one day to unify the visuals. But if I vanish for a few months to redo old art, I’ll get crucified Especially if I end up changing something again right after and have to redo it again.
So for now... let’s just agree to live with a bit of the chaos.