We scale at 1080p; which is why I’m saying you won’t benefit from running the GUI at 4K, but you will incur a performance penalty.
However: on other devices, if you have a 4K windowing system, you are still better to run the GUI at 1080p in almost all scenarios.
For 4K FB, see this post for an idea of the changes that would need to be made.
Cheers