Repentogon mod might help but I don't use it as it doesn't officially support Repentance+ yet.

What I do use is use Lossless Scaling and use framegen adaptive mode which framegens the game at whatever FPS you set it to, so I have it set to 172fps and it keeps it at that no matter how low the game drops. Even when game's native fps drops down to like 30fps, it still framegens to 172fps. The only issue is the game still slows down when this happens, but that's not always a bad thing especially in tricky boss fights, it's basically matrix bullet time ;)