It looks like there is a much faster competitor to MathJax, called KaTeX that was recently released. I know that for some of my longer answers (here and here), edits require a refresh to properly display. Additionally, it can take some time to actually compile/display.
Is cs.stackexchange tied to MathJax or is it possible to switch?
Not that we must switch. I'll admit that this isn't necessarily a massive issue, but it is nice knowing there are options.