I also want to use letterboxing because screen-size is very unique info and I don’t think it has side effect in bad way for my privacy.
But I could not find any official information if letterboxing enabled then RFP is also enabled by default or not. Because letterboxing config name has “resist-fingerprinting” suffix.
If there is no any source/documentation for my question, is there any manual test for me to check locally if RFP is enabled. I want to make sure.
Additionally I want to ask if there is a good source/documentation what differences has RFP and FPP.
No letterboxing does not enable RFP. If you want to test it out yourself, you have to disable privacy.resistFingerprinting and set privacy.resistFingerprinting.letterboxing to true. If you go to a site like duckduckgo.com (assuming you have set your system to be dark mode), it should be dark mode.
I highly suggest enabling RFP if you can though. Letterboxing on its own hardly does anything if not nothing at all. You still have all those other data points part of your fingerprint.
Lastly, if you care about fingerprinting, you should use something like the Mullvad Browser (with a VPN), or if your threat model calls for it, the Tor Browser. Both of them will blend you into a crowd of people which makes it for websites much harder to fingerprint you.
I also want to enable RFP. But it breaks most of the web sites. Therefor I asked about a source/documentation for differences of RFP and FPP. Because people says that RFP is also detectable, if there is no such a big deal (enabling RFP for someone who already enabled FPP and letterboxing), then I will not enable RFP. (Im really curious about this answer)
I read the wiki you sent me 3.3 Overrides but I could not find what is the differences.
