Will it peel the paint if one were to remove them, or would it harm the minitures in any way?

The stickers shouldn't harm the miniature or it's factory paint job.

Having said that, if you've repainted your ships with cheaper/discount acrylic paints, they have a tendency to come off I've noticed. I'm not sure how much sealing the paint would help in that instance.

The only thing to watch out for would be any residue left behind by the sticker after you've peeled it.

Waterslide decals (like the ones you get in model kitsets) always work and if you paint over them with a coat of matte varnish, they won't come off at all. Generally they're so thin that you can paint over them with another colour and you shouldn't be able to tell they were ever there.

I find that testing this sort of experimental stuff on something before doing it on the actual piece you are working on is a good practice.

That way you'll know how things perform before doing it to the final product.

In your case you'll want to try it on a ship you don't intend to use much. But even that could have some error. It seems that the x wing ships don't all use the same type of plastic.

I can't be positive...but I think there's a difference between the plastic used on tie fighters and the plastic used for the hawk.

If you have a spare of the same ship use that as a test piece.