If it helps any, I am seeing something similar. I have not been on line much over the last couple of weeks, but in that time my Brave experience has changed significantly. Here are my particulars:
OS: Mac OS Mojave 10.14.6. Brave: Version 0.68.142 Chromium: 77.0.3865.90 (Official Build) (64-bit). There is a notable lag on browser startup (“notable” meaning 0.9-1.1s). There is a notable lag when clicking “=” for a new window. There is a notable lag after the blank window comes up, during which “chrome://newtab” shows in nav bar, before the Nav changes to “New Window”, then a bit later the stock “Ads and Trackers Blocked” summary window comes up. Then typing a straightforward URL, like google.com, has a similar lag before it renders.
Overall is it takes 8-9 seconds from a new tab to the google.com window rendering. Similar, if maybe a bit let lag seen when clicking on the
x to close the tab.
CPU runs around 8-9% during all this.
Opening the “About Brave” window showed all of these things (6-7s to rendering), plus, mousing over the version info was jerky and blotchy, not smooth. The visual feedback was running behind the actual mouse position.
Chrome works fine. No other apps seems affected. Private windows are also slow. Tor windows are incredibly slow.