What about the wasted space that shows your theme and the name of the web page?
If I wanted minimalistic, I would modify the source code of Firefox and overhaul the UI. Plus, that's so little space that I really don't care.
I'd rather have a
good browser than a browser that tries to be minimalistic.
P-sure Chrome has that built in.
It doesn't, that's just disabling Javascript for certain webpages.
You can do that in Firefox too.