Quit everything
MacOS command line (Terminal.app window); enter:
open -a "Brave Browser.app" -n --args --disable-gpu --disable-extensions --enable-leak-detection --crash-on-failure --incognito
The idea, here, is to somehow get Brave Browser running, from the command line, and using flags that might reduce its thirst for CPU/RAM.
If this test works, then go to, and ENABLE both:
brave://flags/#brave-adblock-cosmetic-filtering
brave://settings/?search=crash+reports
The first - adblock cosmetic filtering - can reduce CPU thirst.
The second - would allow you to get some Crash IDs and send them to Brave Support.
Both of those possibilities, are mentioned in Brave Support replies by “Mattches” - - - who may be interested in your findings.
IF / WHILE Brave Browser is running, be sure to backup bookmarks and whatever else that you can.