As far as frame rate, the original setting prior to FPR14 was -1, which was paint as fast as you can and don't throttle. Anything setting a high frame rate is essentially doing the same thing. This might help some pages but will harm others, and 30fps has been the default since FPR14. See http://tenfourfox.blogspot.com/2019/03/tenfourfox-fpr14b1-available... for more explanation.
Part of the issue could be them restarting the browser to check changes. That will always seem to make things faster because garbage and cycle collection time becomes negligible, even if you don't actually toggle any prefs. The acceleration prefs do no harm but they don't do anything anymore, and I should probably just remove them if people are abusing them like that to make the point clear.
Well no harm done I guess, people can be left to it...even if it is somewhat delusional.
Having access under the hood is invaluable though - the site specific user agent feature you implemented a while back is a great addition to the browsing experience.