Best for PvE solution?

I'm already using Photon PUN for my two games. I'm planning for the new game, but Photon PUN has a lot of issues, especially if there are too many enemies.

I'm only making Co-op games with bunch of enemies (more than 30), and I saw some news that Photon published new stuff like Fusion and wondered which one is proper for my game.

And is there any reference to switching Photon PUN to something else?