I use PL3 to edit the NEF-Files, sometimes also JPG, from my Nikon Z7. I work on an 2017 5K iMac 27" (24 GB RAM and Radeon Pro 580 8GB) with all the latest updates for OS X and for PL3. In general the performance of PL3 is mediocre, compared to other tools like Affinity Photo for instance.
When editing a lot it gets really, I mean really, bad. When working with local corrections (repair) PL3 “thinks” several seconds, before it is showing up with something.
I think PL3 is not optimized to handle 40 to 60 or more MPixel files very well. This performance flaw is a pity, because despite this I really like PL3. Are there plans to improve performance substantially?