I believe that the only two privacy extensions you really need to meet 90% of your privacy goals are uBlock origin + NoScript
uBlock origin is effective because it stops the injection of ads which might contain and inject code. NoScript forces you to look at which scripts you really need for the website to function. Say you visit a trusted site, like your lemmy instance, then you can enable running of javascript by default the next time you visit the site. You’ll be surprised how functional some sites are even without javascript. I did not like the idea of browsers having Javascript: it’s remote code execution and if there’s anything malicious in there and your browser is not patched against it you’re fucked. This way yeah it’ll be annoying when you first visit a site but it remembers your settings for the next time you visit.
No. If you use TAILS then no. The NSA slides leaked by snowden even had a slide showing where they could not gain visibility (I belelieve they called it a disaster to their efforts), and TAILS was on the list
If you use tails correctly, you’re a lot less likely to deanonymize. Snowden was also over a decade ago so we have no way of knowing what’s changed since then.