It's definitely down in a large part to plug-ins. Things like Dark Reader I can understand, but I have no idea why 1Password would cause a 30% performance drop

It's definitely down in a large part to plug-ins. Things like Dark Reader I can understand, but I have no idea why 1Password would cause a 30% performance drop on a site that I don't even have a PW for. My point still stands about going back a page and arrowing up/down the URL bar to select something and having it swap at the last second. Those behaviours are peculiar to Safari and they're really inexplicable from a user perspective. Whether it's related or not, the mobile version of Safari is even worse - going back a page refreshes 95% of the time, when it shouldn't given the amount of RAM iPhones have had for the past 5+ years. The Chromium stuttering on M1 Macs is definitely a problem and I wish Google would get to fixing it.