This is very recent, because just weeks ago Street View was fluid, with 11 extensions active and 48 tabs open (almost all suspended, but anyway).
Now I’ve tried with a clean profile, no extensions, no Brave Shields, only google maps website open, and it’s sluggish either by rotating the “camera”, or specially by “travelling” through the streets, when in other browsers it runs smoothly.
There’s a way to make it work again as before, by going to brave://flags/, searching for Override software rendering list, enabling that property and restarting Brave. Then Street View plays fine again, but the thing is, I always had that flag deactivated and Street View worked normally before, besides that flag may be experimental, I don’t know how stable that is.
Also, in other chromium based browsers, Street View runs fine with that flag disabled.
Please check that.