On both devices I use the same Microsoft account to log in.
Problem is - the Switch theme keeps overriding my desktop. I'm not sure what triggers it, but whenever I boot up my PC it changes the theme and the desktop background to the Acer default theme that I use on Switch. Note my PC isn't Acer. I then change it back to my preferred saved theme and all is fine, until I reboot it the next time.
I do like using the Microsoft account to login (especially using PIN), so I don't want to stop doing that, but this strange problem is driving me nuts. Any ideas anyone?