It's beyond my expertise, I can't generate a state which simulates a clean slate, except buying a new phone and registering a new google account along with it. And barely then, I'm sure they catch on very quickly.
There is a firefox extension called containers (<a href="https://support.mozilla.org/en-US/kb/containers" rel="nofollow">https://support.mozilla.org/en-US/kb/containers</a>) that can be used to isolate different accounts. So if you want isolated accounts then containers for different accounts will help you do that.