After latest system upgrade my Hitman installation was freezing with no way of unfreeze until you quit the game. Here is what i did to help it:

• use the __GL* options from the Proton help page, seemed to do a lot;
• disable compositor during the game runtime (for me it was picom, just kill it and run it again after);
• use gamemoderun (not a built in thing, install it and run games with it, helps a lot);
• use NVIDIA DLSS in Hitman settings, really helped with performance.

I made a wrapper script to run all my games with the parameters, gist: https://gist.github.com/oleksandrzelentsov/0132ff3f6e95dbcf3a8699d9adbf67b1

Then in the game run options in steam i just do game_wrapper.sh %command% -skip_launcher, and similar, for every game. Game performance is surprisingly good now.