I tried Ironfox for several weeks some months ago. I like the project, but it was painfully slow, mainly because it disables JIT and some other things. (Brave also has a JIT-less mode, but I found it to be faster than Ironfox.)

Also, it comes with uBlock Origin preinstalled, which is good, but the devs enable by default a ton of lists, which contributes to the slowness. I suppose that if you have a fast device it won’t matter, but on a low to mid-range device it becomes unbearable. The best you can do is disable the preinstalled lists and use one of the modes recommended by uBlock.