Premiere Pro CC Performance question

[Xorherk]

I have a 3950x with two Titan RTX's with NVME's for storage.  I recently tried a trick I saw a youtuber do where they have a canvas in OBS of 3840 x 1080 and have their game and their face came on that canvas, then in premiere can cut down with crop the recording file TWICE, once to have the game as the main view, then my face cropped down even more to just my head and placed in the corner like a lot of YouTubers do.  So, I end up with 2 streams that are 17GB each of 3.5 hours, but my timeline performance isn't much better than what feels like 12-15 frames per second, possibly worse.  Files recorded as 1920 x 1080 from original are fine and my timeline performance is smooth.  Do I just not have the power with my system to have that kind of file size or do that canvas trick in OBS?  To note, even if I cut Premiere's timeline to 1/4 resolution, it still does not play any better.