Resurrection of old threads is not a great idea, I know, but I just wanted to observe that the new (TenFourFox 4) version available as of late 2017/ early 2018 is the best yet. I keep worrying that bloat will kill T4F, but nope, it keeps getting better. Scrolling in graphics on newspaper websites, etc., is pretty smooth even on piffling Powerbook G4, though I will confess to using uMatrix to help things along.
Now, the truth is that T4F still will not do video, etc., so there are obvious limitations, but overall the browser is very usable, and represents a huge step up from deprecated versions of Safari, not least because it takes advantage of Altivec and comes built for the particular PPC CPU you are using.
Unfortunately, the developer is no longer a 68kmla-er, but maybe he'll see this vote of thanks all the same. Meantime, come back CK! We need the stalwarts back on here.
Have you looked at Activity Monitor to see how fast things are being transferred when you're using tenfourfox? In all likelihood, it just takes a long time to render modern web sites. Even modern Firefox on modern computers is slower than the other browsers. Any machine where running tenfoufox is a relevant idea is, at this point, Not Modern.