Well, you say it is a ‘new macbook’ is it new because you just bought it or because it is newest model but you have been using Brave with it for a while?
You can troubleshoot the problem anyway by using Brave’s internal taskmanager you go to ≡
→ More Tools → Task Manager
Then you can see which Tab or process using most CPU and all, and then you can report back and then maybe there is a workaround or something to do with it.
I mean, MacOS resource monitor is a little more useful than Windows Taskmanager but they are not good to show which Brave Browser Helper (Renderer) is using more resources than others, that’s why internal taskmanager is the one you should use.
I don’t use MacOS but I know that unlike Windows, MacOS and the internal Chromium/Brave task manager does the percentage by core, so 1 core = 100%, where in windows is like doesn’t matter your core amount it is from 0 to 100, so if you got a new Mac and you got a lot of cores, like a 16 cores one, whic means the percentage goes up to 1600% (which doesn’t make sense for computing but that’s the way they did it), then 400% doesn’t seem as much compared as if it was 6 cores computer, so since it is relative it can be still normal or pretty bad.
But at this point it could be anything with the information you provided, it could be anything a Brave is causing when is running in the apple processors or Chromium in general, you know, since Chromium has the whole site-isolation and sandboxing which uses more CPU and Memory, the GPU process, or tabs which are usually the ones consuming the CPU.
If the problem was a tab with Youtube or something, well, it would make more sense, but you could also check brave://GPU because it could be the Hardware acceleration not totally working and it is using only CPU.
Hardware acceleration is crappy in browsers, and browsers don’t fully use it, but it is there for a reason and you can troubleshoot if it is a video site that is causing the high CPU by checking to see if the GPU acceleration is working, since videos is usually what uses more CPU or a WebGL game, or something like Brave talk/zoom/jitsi, if you see it is like youtube or something you can even use brave://media-internals/ to display information about decoders and all that for players and any media playing.
But as far as I know, many Brave team seems to love using Apple computers, often I see MacOS screenshots in commits and issues over Github, so, if it was like a Brave issue, I am sure they would notice and fix it by now.