I plan on uninstalling and reinstalling league to fix some un-relevant issues. However I do not feel like re-applying all my custom video\interface options. I also don't wish to remake my custom item sets for my champions. Which files would I need to save first to keep these custom settings?
3 Answers
C:\Riot Games\League of Legends\Config (installdir\Config)

game.cfg contains the game settings like mousespeed, volume etc. I think this is what you need.
input.ini contains all of the keybind settings that you have changed from the default.
Both can be opened with notepad.
3If you are on a Mac (osx) then, go to:
Applications -> League of Legends -> Right-click the icon -> Show Package Content -> Contents -> LOL -> Config
You'll find the following:
- Champions (folder)
- game.cfg
- input.ini
The show package content

The Contents Folder

You no longer need to manually copy over your client settings as they are now preserved on the League of Legends servers.
via patch 5.22.