If anyone else finds this forum while having PC performance issues, this guide on how to modify your .ini file to unlock and disable certain UE detail settings is useful, and better than explaining it myself.
This works alongside Lyall’s unofficial resolution patch, and is actually the only way I’ve been able to run the game above 10-15fps at a modern resolution (running a GTX 1060/Ryzen 2600X/32GB RAM.)
With luck, devs will have time and see fit to unlock more quality settings in the upcoming megapatch (good luck, guys…!) but until then, hope this helps.