A recent studio update has caused my CPU usage to be 100% on my 2018 MacBook Pro, causing it to get extremely hot and really laggy - even on an empty baseplate.
I can vouch for this as well, opening up studio and letting it sit open with no game loaded (and all other applications closed) averages around 112% CPU on my 2019 MacBook Pro which I got about 2 weeks ago.
It causes the internal fans to kick in, full gear and sound like an airplane taking off pretty much instantly then it heats up drastically. But strangely the fans stop extremely quick after closing Roblox Studio.
Noticed this yesterday while on Catalina 10.15.3, updated to Catalina 10.15.4 and it’s still there. I’ve done multiple cold and warm restarts. I also updated and deleted Studio today, and it changed nothing.
My situation is pretty much exactly like OP’s.