Hi, it's a strange workflow issue. I have also seen 4K videos online, however not much information on how to do it.It's a question I've been asking also, and I know it can be done (because I've seen others do it) but I dont know how. How do you capture a 4K or even 8K screenshot if your display is only 720K or 1080K? And besides capturing screenshots can you also make videos at a resolution higher than that of the display in the same way?
How do you capture an animation sequence if you cannot see most of the screen? It seems this is still an issue in the PRO version. The workaround on the PRO is that you can record the camera path. Set whatever the resolution to whatever you like, and record that in the windowed display.
It seems working with a cropped windowed view is the only way. For example, you can set your windowed display to 4K or 8K, and press F11 (Shotcut to take a screenshot without all the controls /GUI present). That will work fine because even if you can not see the rest of the 4K window on your monitor, you'll be taking a full single frame screenshot with the F11 shortcut.
Now, the issue I think we both have is creating 4K (or above) videos, where you need to fly manually and capture that. I have found out that changing the capture image sequence in TIFF or TGA works very well, the system won't lag as compared to using JPG or PNG to output the capture sequence. Alternatively, you can use a screen capture software which is what most people are using.