is there a way to make spacemacs faster for large documents and or really long lines?

@alexkeyes I would look at aggressive-indent-mode as the first candidate. SPC h d v in a clj buffer, and enter aggressive-indent-mode to check its status. If it’s on, try shutting that off first & see how it goes. I like it a lot, but I at least have paid a high perf price for having it on by default.

I’ve found it a bit tricky to disable, but try adding (global-aggressive-indent-mode nil) to your user-config.