Don't use Fasterfox. It tweaks many settings that frequently result in performance regressions. The default networking-related settings are set the way they are for a reason.
That is of course not the case.
For me, currently, my setup is the best browser I've ever used.
Some forks have clear advantages, are well maintained and trustworthy.
There are numerous reasons to maintain a user.js file also, not just performance reasons.
Indeed, report issues to Mozilla directly, but that isn't inconsistent with using a fork and maintaining a user.js