Hi, and welcome!
I'm on Mac Air Early 2015, Catalina, R 3.6.2, RStudio 1.2.5019 with Preferences | General | Advanced | OS Integration | GPU autodetect, blacklist and driver workaround. Installing PanelMatch had no effect.
RStudio 1.2.5033 is just released, and I'd suggest falling back to that from your current version (I'm not even sure that there is a 1.3.667; at least, I couldn't find it.)
And don't panic. At worst, you can run free cloud instances if you can keep your total resource demand under 1GB!