These are the basic basics for tweaking FF's about:config. There are many more. Try these and see how you fare...
layout.css.visited_links_enabled set to false;
geo.enabled set to false;
media.navigator.enabled set to false;
media.peerconnection.enabled (WebRTC) set to false;
network.http.sendRefererHeader set to 0;
privacy.resistFingerprinting set to true;
privacy.firstparty.isolate set to true;
network.dns.disablePrefetch set to true;
network.prefetch-next set to false;
webgl.disabled set to true
Don't forget to also use something like uBlock Origin, Token Tracker Stipper, and Decentraleyes. Pass is all through a Pi-hole and VPN and you're pretty safe. Make sure your VPN does not expose your NAT'd IP with WebRTC. Both uBlock Origina and ScriptSafe can help with this, as FF will sometimes crap all over its about:config settings with updates.
I don't seem to suffer from slowness with my FF setup. My home connection is 400Mbit/50Mbit unlimited. I surf heavily/code/SlingTV all the time. I also keep a similarly locked-down instance of Vivaldi on hand for email and banking only. Everything else goes through FF or OpenSSH.
Most of the time in the Netherlands. Sometimes in Texas with IT friends. We do VPN sharing and passthroughs to mix it all up. Hence my wanting to set up more permanent solution like hosted, heavily VPN'd remote desktops with revolving IP addresses changed with a cron job. but one standard set maintenance port that never changes and likewise never used for joyriding. That IP would be accessed via OpenSSH authenticating to Radius/Kerberos.
You don't need Tor to do this. Tor is slow and frustrating.
I use a heavily-modified Firefox instance over a VPN with uBlock Origin, Privacy Badger, Disconnect, No Coin, Script Safe, Token Tracker Stripper, Neat URL and too many about:config edits to mention.
I do recommend disabling http/s referrer, CSS visited links, and others as can be learned online.
In addition, I pass all of this through a remote computer with a Raspberry Pi/Pi-hole instance. This has worked well for me for a couple of years. As I have no real social media accounts, I'm not building any meaningful profiles. Accounts like HN or Slashdot don't get any real info. I also don't add any apps to my iPhone. The apps that ship with the device are all I need. I can pass all of my phone's traffic through the VPN/Pi-hole instance and keep relatively safe. Being with T-Mobile means I get unlimited data so I don't need to connect to potentially hostile Wi-Fi.
I rather enjoy the "cold war" between the corporations and the security-minded. There are so great add-ons to uBlock and other add-ons that completely bypass the complaint scripts of using adblock.
Another quick way to get past fake paywalls or complaining pages is to use Startpage's proxy or even Google's cached link. I've set up so many people to use this set up and they are thrilled.
I am thinking of setting up remote desktops that can be accessed by friends and family that are VPN'd, Pi-holed, and with other security features that hide their real IPs, etc.
Like most IT guys, I block everything possible: cookies (whitelist), CSS history, ads, beacons, tracking of all sorts, http/s referrer, webrtc, browser fingerprinting, DNS prefetch, and much more, passing all of this through a personally-controlled remote non-US VPN that logs absolutely nothing. Ads? What ads?
I pass all traffic through this, including mobile devices, so protection even when away from home. Is it 100% foolproof? No. But I have yet to have issues, and Google and others have zero profiles on me, as I have no accounts with them or Facebook, et al. It's nice to be able to be relatively off-the-grid while still taking advantage of what the Internet has to offer.
layout.css.visited_links_enabled set to false; geo.enabled set to false; media.navigator.enabled set to false; media.peerconnection.enabled (WebRTC) set to false; network.http.sendRefererHeader set to 0; privacy.resistFingerprinting set to true; privacy.firstparty.isolate set to true; network.dns.disablePrefetch set to true; network.prefetch-next set to false; webgl.disabled set to true
Don't forget to also use something like uBlock Origin, Token Tracker Stipper, and Decentraleyes. Pass is all through a Pi-hole and VPN and you're pretty safe. Make sure your VPN does not expose your NAT'd IP with WebRTC. Both uBlock Origina and ScriptSafe can help with this, as FF will sometimes crap all over its about:config settings with updates.