Firefox best practice for security

I am very privacy and security minded lately. I use (and like) Firefox as my primary browser and use Chrome only for Facebook. I do not use Edge. I am on Windows 11Pro.

My hope is that Facebook on Chrome can not mine as much data because all of my other web use is on Firefox, but I have no way of knowing if that is correct.

I also want as much privacy as possible without running through hoops. I just put a VPN on my Asus router. I actually have a main router for most smart devices, TVs, and such, and a second router plugged into the first router that routes through the VPN (the VPN is built into the router settings). I believe my data is encrypted from my router to the VPN's server, but ultimately it leaves from my main routers IP address.

I am not in California, but I use a VPN server in Los Angeles. When I go to sites to check my IP address and location, it is not my actual IP and says I am in Los Angeles (like it should).

We know websites mine data. Can websites on one browser mine data from another browser?
How can we be more anonymous without loosing much functionality or ease of use?
Are browsers linked to a machine code of your computer? Is there any way to bypass machine and personal identity?
Does a Private Window protect you from what is sent, or only what might be saved locally?

Although I am not doing anything illicit, I don't like the argument "if you are not doing anything wrong, you have nothing to worry about". Data is BIG business!

I don't want to go through extreme measures (like an Onion browser) or break websites. What methods do forum members use to best protect their privacy and identity? I specifically want to use Firefox, but it could be a variant, extensions, settings, or what ever you use. I look forward to your thoughts!

Thanks!

I'm still interested in what other users are doing, but in the meantime I just found this. Looks helpful.

The most important for me are:
'user_pref("privacy.resistFingerprinting", true);'
'user_pref("browser.send_pings", false);'
'user_pref("dom.battery.enabled", false);'
'user_pref("dom.event.clipboardevents.enabled", false);'
'user_pref("extensions.htmlaboutaddons.recommendations.enabled", false);'
'user_pref("extensions.pocket.enabled", false);'
'user_pref("browser.urlbar.richSuggestions.tail", false);'

potential breaking may occour with these:
'user_pref("privacy.firstparty.isolate", true);'
'user_pref("privacy.firstparty.isolate.block_post_message", true);'

I've posted this before - this guy has some suggestions (with brief explanations) for improving Firefox privacy-
Firefox Privacy
He cautions that some changes will break some sites.

There is a plugin called "Firefox Multi-account Containers" that's supposed to prevent sites from accessing cookies, etc., from other sites. Their product description says it's like using a separate browser for each web site you set-up.

For privacy, make sure you enable secure DNS in the Settings -> General -> Network Settings (Enable DNS over https).

You can also arrange this at the system level. There is a tutorial on this site.

This will encrypt the DNS lookup of the sites you visit (otherwise it is done in clear text and can be captured by a bad actor). Also pay attention to ECH (Encrypted Client Hello) that will be coming in the near future to further secure your web browsing history from bad actors.

on my phone I use VPN with DuckDuckGo browser.

Some new settings i`ve been using:

user_pref("privacy.resistFingerprinting", true);
user_pref("browser.send_pings", false);
user_pref("dom.battery.enabled", false);
user_pref("dom.event.clipboardevents.enabled", false);
user_pref("extensions.htmlaboutaddons.recommendations.enabled", false);
user_pref("extensions.pocket.enabled", false);
user_pref("browser.urlbar.richSuggestions.tail", false);

# Disable updates
user_pref("app.update.auto", false);
user_pref("app.update.checkInstallTime", false);
user_pref("app.update.auto.migrated", false);
user_pref("app.update.service.enabled", false);
user_pref("app.update.BITS.enabled", false);
user_pref("app.update.background.interval", "999999999");

# Disable cross-domain cookie access
user_pref("privacy.firstparty.isolate", true);
user_pref("privacy.firstparty.isolate.block_post_message", true);

# DNS-over-HTTPS (DoH) encrypt the communication between the client and the resolver to prevent the inspection of domain names by network eavesdroppers
user_pref("network.trr.mode", 2);
user_pref("network.trr.uri", "https://dns.google/dns-query");
user_pref("network.trr.bootstrapAddress", "8.8.8.8");

# Enable Encrypted Client Hello (ECH) on Firefox, to prevent TLS from leaking any data by encrypting all messages;
user_pref("network.dns.echconfig.enabled", true);
user_pref("network.dns.use_https_rr_as_altsvc", true);