I don't think that the right question is to ask about the XReal One or One Pro, any more than it would be to ask about a monitor, because they aren't storing an image and projecting it into 3D. There's an accessory, the Beam or Beam Pro, that does the 3D projections.
https://old.reddit.com/r/Xreal/comments/14vdrps/maximum_input_resolution_of_the_beam/
From Xreal's tech support:
Although Beam does not set a limit, the final display size is determined by the glasses. The resolution of the XREAL Air is 2*1920*1080p. The spatial screen changes in proportion.
I'm sure that there is some limit, if due to memory constraints, if nothing else. And USB-C bandwidth will limit what you can be pushing relative to the framerate. He might mean that it's not really a practical limitation, though.
This guy apparently ran 4k input:
https://old.reddit.com/r/Xreal/comments/15tke6a/display_4k_or1440p_with_xreal_air_beam/
The challenge is the physical limits of AR glasses' bird bath optics. Past a certain screen size or zoom, you will get the borders, and it will look like you're looking out a rectangle window.
But you can "explore" 4K video with your 1080p glasses with 3DoF. Just don't expect an IMAX experience with huge FoV. So, in one of my videos, I test this with my Mini PC that was connected to my 4K TV in 4K resolution and simply hot swapped over to my XREAL Beam setup. Windows was still in 4K and my Shadow PC session was still in 4K running Diablo 4.
I didn't turn up a straightforward specification with a couple searches, though. You're probably going to want to be looking for the input resolution to the Beam.
EDIT: It sounds like they also have some software package, Nebula, which can act like a Beam and have the PC do the projection.
https://old.reddit.com/r/Xreal/comments/16kvw4f/do_i_need_beam_if_i_want_to_use_the_airs_mainly/
I’m planning to buy AR glasses for remote work as a software developer. Do I need beam to pin the displays in place without them following my head?
Hi. If your computer is compatible then the Nebula app can allow you to do it without the Beam. I'd test that first. The Beam's image is a bit more stable though. Some care (I don't), others are very sensitive to it. So, YMMV
I could believe that with Nebula, there isn't a software-imposed limitation short of whatever your desktop can handle, but I don't see a hard statement on the matter.
Might contact Xreal directly.