It has included some privacy measures to resist fingerprinting like letterboxing and has more privacy focused search engines as default like searx. Also it takes out some firefox utilities like pocket which I don’t really use
As for Mullwav browser I’m not really sure, it seems to be another reinforced firefox like librewolf
For incognito browsing I recommend Librewolf, a firefox fork. If you want anything more secure, you should start looking into tor
How I wish a chat privacy law could be passed to make more difficult to continue eroding our rights.