I can see right there that Brave is actually using less CPU than the activity monitor itself although I do believe that you see spikes as you’re describing.
You said you tried disabling HWA and extensions – can you try browsing/viewing video content on a new profile (
Menu --> Create new profile)? I’m wondering if there is something specific to the data you have in your profile that is clogging things up.
You can try disabling
Hardware Acceleration and see if that helps, but I actually would suggest the same thing I suggested @HannahRosen – try creating a new profile and see how it performs. It’s more than likely you have some “bad data” stored in cache and it’s causing the slow down. Testing against a new profile with no data, extensions, history etc will rule out whether or not the issue is related to Brave itself or some data contained within it.