4. If I can locate one, would it be possible to add another Pink Streaked Wrasse to my current one? I know that some people keep them in pairs/groups, but I also saw that wrasse don't "pair".
I have two pink streaks. I had the original of the two for ~1.5 years and was pretty confident he was a male. Anyways, I saw a tiny emaciated pink streak at my LFS and it looked like a female to me, or at least a tiny juvenile. I told them I’d buy the tank I was looking at if they gave it to me.
I added the little one at night, and by the morning he had already found the small one. Here’s a pic from the next morning where I saw he’d found her.
They've been inseparable since, if you see one, the other is somewhere nearby. So I think you have a decent chance of success if you can get a small one. Especially in a larger tank where they have their own space given (as someone else noted) they might tolerate the other more if they don’t bond with eachother.