Most people call it either slow or medium pace, but that's pretty subjective, so for a general idea: the usual pattern is that the carnival visits a new world every month, with one big mingle log for that world that everyone can tag into for that period.

Sometimes there are mini events between or during those visits, and players can post their own logs whenever they like. Most events are optional, even a lot of the world visits (your character can hang around the carnival instead if you like). Since there's a lot of leeway in what you participate in and how much, it's pretty easy to control your tag-load without worrying about falling behind!

I think it's pretty backtag-friendly! I see people backtagging events from past months a lot, and I'm always cool with getting tagged at any time!