FWIW, the Developer Edition feels pretty lean and mean. I haven't tried since I am a web developer, but it looks like you can remove most or all of the parts that make it web developer-y if you are so inclined.
Mozilla's business model needs users who can't figure out how to turn off Yahoo search. That pays for their new Firefox offices on the waterfront in San Francisco.[1]
[1] https://www.google.com/maps/@37.7895991,-122.3883498,3a,36y,...
1) Firefox without DRM, without lockdown
2) Firefox without DRM, with lockdown
3) Firefox with DRM, without lockdown
4) Firefox with DRM, with lockdown
...for every language?
In any case, if the specific combination of features you want is missing, the option to build from source is always there. (At least on Linux, building Firefox is also pretty easy.)
However, "without lockdown" is going to be an "unbranded browser."
So likely you will see two folders, something like this:
/browser/release/
1) Browser with DRM (no lockdown)
2) Browser without DRM (no lockdown)
/firefox/release/
1) Firefox without DRM
2) Firefox with DRM