On Edge and Firefox I have to let it read the entire page and cannot stop it or go back to anything else it won’t read anything else.
It sounds like you may have skim reading turned on. Press NVDA+ctrl+k, and look for "allow skim reading in say all". If that is checked, uncheck it. I bet firefox and whatever else will work fine after that.
You might also want to press NVDA+ctrl+b, and uncheck "Automatic say all on page load".
