I've been having this issue with X-Code for years and have never found a fix. I've seen many people post this issue but no solutions that work.
When typing in X-Code, ever few letters I type the editor just hangs, sometimes the rainbow beachball spinner even comes up. Just pressing return takes a second to complete. Any ideas? There's got to be a fix for this
I have had this problem when I have devices set to sync over wifi. It doesn't matter if I'm actually building and running or if I've just opened Xcode and am trying to edit files.
I can (usually) make it go away by removing one or two devices that connect over wifi from the list, or by plugging them in via actual wires. I don't know if that's the actual problem, or if it triggers something else deep in Xcode, but maybe the same will work for you.
I have had this issue (lag / delay when typing in Xcode) with my wireless Apple keyboard, the usual off/on cycle seems to fix it for me.