This is a topic of mine which may be related. There’s a general issue in UE5 that the screen percentage/resolution scaling settings are so overcomplicated and convoluted most people are never actually aware of what real resolution their game or project runs at. It changes wildly based on way too many factors.
So for example in Editor, you may see extreme flicker because TSR is upscaling from something like 60% of the original resolution. Even worse, just minimizing/maximizing the viewport using F11 key can be changing this screen percentage scaling on the fly.
Out of the box, in editor, it can be either scaled or not depending if you touched the in-editor scalability settings at least once, as they default to project settings, but if you touch them, even just once, the screen scaling will snap from the project settings based one to scalability preset based one.
Here’s an example of the default with maximized editor viewport rendering just 60% of pixels:
It’s been giving me severe anxiety for years now, never really being sure about what resolution the editor, PIE and packaged build runs at. It just changes so wildly…