Wasn’t really following whole of the discussion, but I feel like you should be told not to stop, drop this engine, and transition off to something that actually offers both look and performance.
This engine is dying and getting worse with every “upgrade” they release, at a constant pace.
It isn’t capable of running anything “realistic” at a satisfactory speed not even with top of the line equipment.
In fact, is not even really capable of doing raytracing correctly, so much so that nvidia has to go out of their way and release their own branches.
For realistic looks and performance, in my opinion -because after all it’s just an opinion - go to CryEngine.
Since you are just starting to learn, you won’t miss out on much.
If your intent is to just render a single screenshot, or to make a rendered movie, then I guess ue4 can work, since performance doesn’t matter with those.
You’ll probably spend over a day on a 10m scene at 4k though.
Even 1080p logo work takes around 10m to properly render sometimes.
If your intent is to generate something playable - then UE 4.18 or even before is more likely a better choice.
I’d still suggest pulling the source and building from it in all occurrences.
Particularly since currently .27 is beyond broke off the launcher.