For myself I would avoid most mods entirely. I dont count mylar as a mod but would carefully consider its use.

For sure dont mod in a way that cannot be reverted to stock invisibly and easily.

If you want to add something or a bit of bling and you like it- its your game do whatever the heck you want. Just beware resale will take a hit if your mod is not reversible and that they basically dont add value to a game (who cares) so dont view them as an investment.

Toppers are not “mods” and can retain value if well done or widely known in the community.

Also- as others have said- wax regularly and check pinballs for wear and replace or tumble to renew whenever they look scratched.