Good questions! Here is a video about removals.

I have 2 browsers open, computer offline.

The left removes nos.lol and the right adds nostr.wine.

Then computer goes online,

the left gets nostr.wine added and the right gets nos.lol removed.

They both converge to the same result list/set no matter how much remove/add you do.

Operations can happen out of order, very old, offline, doesn't matter.

Does this address your concern?