For sites you visit occasionally, it's better to enable tab isolation (use the containers feature) and then enable JS only for that domain (note the difference between allowing JS from that domain in any tab, vs only allowing that tab with that domain to use JS, you should do the latter)

https://addons.mozilla.org/en-US/firefox/addon/multi-account-containers/

If you're switching to a different browser you may as well use the same browser but a second clean profile and use private tabs so it doesn't retain history. Using private tabs in your main browser profile does also help but isn't perfect because there's still some metadata leaks occasionally.

Using a different browser could ironically make you easier to track - how unique you are is the main signal used to track you (user agent, OS, language, etc), and going for an even more rare config will help their tracking even if you delete session cookies. Especially if they have a tracker across multiple domains you visit from different browsers from the same IP, with similar device fingerprinting results across browsers. That's a strong signal those sessions are linked. You want to NOT stand out to maintain your privacy.