is there any overlap between mers (the fandom) and those that get to perform as merpeople sorts at like, here in florida we have weeki wachee springs state park that does mer shows.
Absolutely! There is actually a decent market for "professional mermaids" at aquariums and birthday parties and things of that nature. While I can't say for certain that any of the mers in Weeki Wachee specifically consider themselves part of the fandom, I definitely wouldn't rule it out. I would think of it in the same vein as how there's an overlap between furries and professional mascots.
Speaking of Weeki Wachee, I absolutely want to attend their mermaid summer camp someday, although I've heard the water is very cold