I think minor tweaks to smooth out the game play and fix issues so it plays as it should is good. I don't move posts/add rubbers to make game play easier. Changing game settings is OK depending on what you do. I don't make it easy to get a bunch of extra balls or change from 3 to 5 ball play. But I make it fun. An example is what I have changed on Kiss. I set the extra ball to 1 lit instrument. You still have to get 23 more for a second extra ball. I changed the grid to 1 completion to get HOF multi ball. And lit instruments carry over from ball to ball. These minor adjustments still keep gameplay pretty close to stock as far as overall rules go but makes it fun for me at home.

As far as mods that do nothing for game play......each to their own. I have a few tasteful mods such as speaker light kits but I am not into gluing every little nick knack possible on my games.