August 2020 iMac 27-inch slow - EtreCheck report attached

I've been having a lot of problems with my machine. Screenshots below of system details and activity monitor below. I mostly use Adobe InDesign, Illustrator and Photoshop, as well as Safari, Apple mail & messages.  

I'm maxed out on 3rd party RAM (OWC) but my performance has been super sluggish almost from the start. Now it's even more sluggish -- delays when I move cursor in Adobe programs, lots of delays in rendering within Adobe programs, and big lag when I type in all programs. Even when I close all the programs and restart, all the slowness persists.

I ran Etrecheck and report is attached. I'm not technically savvy, and wondering if anyone can point me to the issue(s)? 

(Also, yes, I know I don't have Time Machine running -- I had some problems with external hard drive, which I'm currently replacing so I can restart that process.)

Thank you so much.