Massive delays after minor (?) edits and/or task switching

Hey there,

haven't used PP in a decade+, so I'm basically back to basics.

System Info: 
Win 10
128 GB RAM

4x M2 Key SSDs for scratch (1 TB disk dedicated for cache) & clips
Dual Xeon CPUs (lower grade)
Quadro M5000 GPU (8GB)

PP version 23.6.0.(Build 6s)

Project Info:
7x tracks 4K ProRes
2x tracks FHD ProRes
multicam

2 audio tracks (1 disabled, for reference, , all others "deleted")

1 main sequence containing one nested sequence, and that one containing 2 straight clips and 7 nested 

Problem info:
no crashes or freezing, super smooth playback at 25% res, but if I, e.g., create a keyframe, it takes several seconds to process and letting me "touch" the interface again. Same goes for returning to PP after task switching (web browser), or opening a source clip inside PP, the latter taking especially long to open. 
Once PP has "recovered", I can scrub and play back like it's nothing, but getting there is a pain.

Steps taken so far:

1. deleted all cache
2. rolled back to the latest studio GPU driver (tried multi monitor, just caused problems, GPU probably isn't related)
3. restarted Premiere
4. closed all other software, using iPad for all other necessary tasks
5. ran the Adobe Premiere diagnostics tools with no results
   
   Is this something I have to live with for now? It's rather debilitating. PP works way, way smoother than AE, which I constatnly use since years, but those "thinking breaks" in between are frustrating.
   
   I tried searching, but Google mostly turns up articles to "slow motion", "filming reactions" and hardware related issues, English isn't my native language, so I'm out of otions.
   
   Thanks!