To improve my Firefox experience, I use a combination of extensions and a special configuration to improve security, privacy, and performance. I will be writing about each of these improvements. And yes, I haven't written much, it's summer break, I am very busy with IRL stuff!
For extensions, I use Chameleon, Poper Blocker, FoxReplace, NoHTTP, and the ever so popular uBlock Origin. I also use a mix of "Container" extensions, Google and Facebook containers.
Chameleon allows you to change your user agent (I don't use this) and spoof details like your screen size and headers (I use). I use Poper Blocker to block pop-up's when I have to download files on ad filled file sharing websites that blast you with pop-ups, it is also good to stop worthless VPN shill ads on torrent websites. NoHTTP blocks all HTTP requests and if it can't replace to HTTPS, it will not load the page at all. uBlock Origin is no questions asked, the best blocker extension I have ever tried.
I use FoxReplace to protect personal information on screenshots, as the extension can change text fields to other text fields of your choice (like a fake address or to blank out text entirely). You should try some results out for yourself!
I use a slightly edited version of the Librefox config, which has a couple changes. You can download the Librefox configuration here: click
My edits include enabling U2F, Encrypted SNI, and DNS over HTTPS. These can be accomplished by:
DNS over HTTPS (DoH) allows you to encrypt your DNS requests by HTTPS for extra security and privacy. An "ISP association" in the UK called Firefox an "Internet Villain" for allowing DNS over HTTPS because of it's enhanced privacy features, then withdrawed it because of backlash, eek! (click). DoH also helps to improve performance, and is also used by popular DNS services like Cloudflare and Google DNS. Quad9 is my personal favourite.
Read more about DoH here (source: Sophos)