with cache folder you are talking about the customs folder where the game is located?

you can freely delete the inside of it, as it only stores the textures and items of people you have /dl'd or been in a mutliplayer room with.

means when you start the game again you will need to re-download the textures and items once you are in a room with them. could become somewhat an issue if you are playing on a data capped internet connection.

your game wont break, it will still work without issues.