Hello, the DMX 512 standard can only handle 32 physicals DMX in/out connections on ONE single DMX daisy chain, this number can be increased when you use a DMX Splitter like our D6 Branch: https://www.adj.com/d6-branch
but as long as you are not connecting more than 32 individual fixtures in one single line, it should hold up.
In terms of the DMX operator, you are at a limit of 32 DMX channels PER fixture, its basically how the channels are broken down and split up between fixture buttons, but you do not have a FULL 512 channels on a DMX operator, most are 192 channels max.
To directly answer the question in bold, there is no limit on how many fixtures can be using the same address, I would believe that even 32 fixtures using the same address would be ok, but once you exceed 32 on the same DMX line, you will get weird DMX data issues, I would even play it safer and try to not use more than 25 per run of DMX daisy chain.
Does this make sense?