The Mojavi downgrade might make sense, but the Knowledge Base document doesn't say anything about Studio One or Capture. As you have Studio One 4.5 already, why not just try?
If you want an answer from PreSonus, open a ticket with Support or ask in this Facebook group:
Presonus StudioLive Mixer Users
https://www.facebook.com/groups/236075319847351
This is the relevant part of the Knowledge Base article:
Apple macOS X 10.15 Compatibility Statement
https://support.presonus.com/hc/en-us/articles/360034790891-Apple-macOS-X-10-15-Compatibility-Statement-
Universal Control 1.7.6 - [Updated: 12-4-2019] - for FireWire products still work on Mac OS X 10.8.5—macOS 10.14 Mojave (Windows 7, 8.1, and 10, as well as). However, it will not be available on macOS 10.15 Catalina or future macOS versions. Users of these products are advised not to update their systems beyond macOS 10.14 Mojave:
StudioLive 1642
StudioLive 2442
StudioLive 1602 Classic
FireStudio Project
FireStudio Mobile
FireStudio Tube
FireStudio Lightpipe
