Encoding is not an issue here, imo. Decoding can be, most likely because of VFR (variable framerate) sources. Even normal CFR (constant framerate) tracks can stutter if there are many of them overlaid, as in your case. You may try these steps to fix the issue (assuming it's 'fixable' at software level) :
1) First and foremost manually clear media cache - close Adobe PP/AE/ME, go to cache location and clean/delete folders: Media Cache, Media Cache Files, PTX, Peak Files.
2) If #1 not help - try to turn off Hardware accelerated Decoding in Preferences > Media... Remember to clear media cache each time you change this settings, also after any app/driver update as well.
3) Transcode all your VFR footage into CFR. Things like iPhone-, ScreenRecordings-, Zoom-, Twitch-, YouTube- videos, etc. Tools people use for this: Handbrake, Avidemux, ffmpeg/Shutter encoder, nvencc, or even a build-in Windows editor.