Agreed, but you still need a confirmation on the quit button to ask if you are sure you want to quit without saving.

If you copied over your home user folder there may be some permission issues in the hidden directories where apps store their settings. If you suspect anything in your user directory might be an issue test creating and logging in with a new user account and see if everything works there.

Sounds like a permission problem from migrating files over, run steam from terminal to see precise errors.

My guess would be to play games smoothly that are so horribly un-optimized they run poorly on all hardware.