Due to CPU issues in Catalina updating to the new iOS will drastically reduce your ability to play multiple accounts at the same time. Yesterday, I had 8 clients logged in using Mojave no problem, today on potato mode >2-3 clients bogs everything down due to huge CPU usage.
TBH ccp should make an announcement on the launcher for the well being of anyone who cares to play eve and has not updated to Catalina yet.
I’ve had a hell of a time running a single client with Catalina. I’ve got an iMac without a dedicated video card and ironically enabling dx9 and “hardware rendering” has improved things. No idea if this will help with your multi-client situation but thought I’d throw that out there.