I've been playing on the Xbox for a long fortnite.
As far as I know, you only get opponents who also play with controllers.
Now I would like to test the whole but s.PC with my account, but now is the question if I do not like the PC and I then back on the console games I get then PC players as opponents, since I myself sometimes synonymous with it played?
So basically, it's more about what input devices you play with.
For example, if you play with your mouse and keyboard on your Xbox, you'll get PC opponents (even now). If you play with controllers, consoles opponents who also only use controllers.
So you have with the change from X-Box to PC and back again, no advantage or disadvantage.
Have fun playing