Two things- there are many flasher wrasses that are similar in appearance, but not identical. I doubt you found a red tail flasher P. rubricaudalis for $30 as they are fairly uncommon and typically command 3 or 4 x that price. Still, many $30 flasher wrasses are gorgeous and I have no doubt yours is too.
Yes you can add more than one flasher, and yes they will fight, but that is when they flash to each other It is rarely more than colorful displays. I'd also suggest finding some females which adds to the show.
Mike when I first met u I had a bio cube and hated sps lol as soon as i saw ur tank it in all sincerity changed my life i was blown away i couldn't believe my eyes that u had all those corals grown out looked like a real reef now I'm running a 220 ! Hopefully one day it will be half as nice as urs I'd be thrilled!