I haven’t bought the game yet, but I’ve been told this guy’s setting list on ProtonDB is supposed to help a lot. Some people are also reporting success with replacing their engine.ini file with optimized ones from mod sites.

Also apparently changing graphics options on the game leads often leads to bad performance issues for that session. After changing settings, if it seems like the game is running worse, you will likely need to restart the game to see how well it will actually run with the new settings.