few more steps to try then:
1) 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) Toggle off hardware accelerated Decoding in Preferences > Media... Remember to clear media cache and restart the app each time you change this settings, or after any app/driver update as well
3) Reset workspace: Window > Workspaces > Reset to saved layout (or just switch to different one)
4) Try on/off "Mercury Transmit" option (Preferences > Playback > Enable Mercury Transmit)
5) Make sure that NVidia G-Sync/ AMD Freesync is off in driver control panel
6) Make sure you are using NVidia 'Studio' driver and not 'Game ready' one
7) Reset app preferences: close all Adobe apps, go to My Documents > Adobe and rename folders Premiere Pro / Adobe Media Encoder. Now start the app while holding Shift+Alt, open your test project and see if there is any improvements.