DSR is a technology for rendering your OS and programs at a higher resolution than your monitor supports. Everything you see onscreen is rendered at the DSR resolution, then down-sampled to your monitors native resolution before output over a video cable. Using DSR, you should be able to record native 4k footage using something like OBS for screen capture and upload to YouTube provided your rig is fast enough to run a game and record in 4K simultaneously. Using external hardware to capture video (like a capture card or a separate steaming PC) would result in footage at your monitors native resolution.
Edit-Did you ever find a solution, OP? Were you able to record native 4K footage using DSR? Just wanted to make sure you...