I recently found out that iPhones shouldn’t be charged to 100%
And yet, iPhone users have been charging their iPhones to 100% for 15+ years with no problems.
there you can set a limit but it must be charged to 100% first to set the limit
Not correct. The battery was already charged to 100% during the manufacturing process.
Here is a fact that surprises many users.......even though you might have a charge limit of 80% on your iPads, the battery will still charge to 100% "occasionally". You have no control over this. The only real question is how often "occasionally" might be.
When I tried Charge Limits, I found that "occasionally" could be as much as 3-4 times a month. Some users report less and some report even more. Here is the quote from the Apple Support document on battery performance. I added the red border to make the text more visible, since it is much smaller text and much lighter text than the rest of the document:

My opinion......Charge Limits are more of a gimmick than anything else, but that might be another discussion.