I have buddy bearings with the zerk fittings. How does that work if I upgrade my rims? Do I have to find rims that accommodate those and do they have to show?

Nobody?

I would think you should be fine and should have some sort of removable cover if they dont show so you can check them and add grease as necessary. They have nothing to do with your rims.

I have aftermarket rims on my trailer that have a hole big enough the oil bath hub sticks thru them. Then a cap is rim covering it all. I'm sure it's the same for Bearing Buddies too.

Thats what I was thinking but it seems like I've seen set ups with out the extended hub or hub cover. I guess that may have a different off set that would allow a flat cover.