Everything related to your games, except save game is in:
/home/username/.PlayOnLinux/
Your fonts, icones, ressources, wine, wineprefix and shortcuts are all in this directory.
You "could" copy the .PlayOnLinux directory, but each game has shortcuts to your Documents, which means copying .PlayOnLinux could copy your entire Documents as well. In the past what I have done is copy the "drive_c" for each games wineprefix:
/home/username/.PlayOnLinux/wineprefix/gamename/drive_c/
This way on the new sytem you can:
- Create the wineprefix for each game
- Restore the "drive_c" folder for each game
- Restore the shortcuts, wine versions and icones
I have several Linux Mint 17.3 computers and I have migrated games from one machine to the other this way and it won't touch your Documents and files.
As for Save Games, those can existing in several places depending on the game. Some automatically create a "My Games" in your Documents. Check there. Other older games create saves in:
- drive_c/users/appdata/local
- drive_c/users/appdata/roaming
- drive_c/documents and settings/local data/application data
- drive_c/documents and settings/application data
Sometimes the saves are in the game folder it-self. So make sure to do research on each game and see where your save games are.