“Discovery requires experimentation”

The Mind Stone didn't give them powers, it just unlocked dormant powers. A cosmic energy jumper cable for their X-Gene battery, maybe?

So r they sort of mutants?

Disney's deal with Fox had the condition of them not being mutants in the MCU, so no they can't be mutants.

I think that Deal is nullified by now.

It has already been established that Loki's scepter gave them their powers. Even if mutants can now exist in the MCU, Wanda can't be a mutant. The comics had even retconned her and Pietro as not mutants but got their powers from the High Evolutionary. And the comics retcon more stuff than the MCU because they've been going on for decades, just a few off from a century and writers need to keep things interesting, so don't expect Wanda to be retconned into a mutant in the more expensive MCU. I actually thought it was weird they retconned the kid in the Iron Man mask to be Peter Parker when they couldn't use Spider-Man in Iron Man 2.

@SeanWheeler That's just what the people in the MCU believe. But only she & Pietro survived exposure to the Scepter, whereas the other volunteers all died. Also, I believe Marvel stated in one of the books (Wakanda Files, maybe?) that the Scepter unlocked what was within. So now that they acquired FOX, they can elaborate more on that; Wanda & Pietro had dormant X-Genes, a 100 or so Sokovians volunteered for Mind Stone experimentation, they all died... Wanda & Pietro survived.