There are many, here is a nice tool for you to check out what is there: https://lemmyverse.net/

It certainly needs an experimental phase, I was just doing research and checking out instances and whatnot first few days. You might find this tool useful for browsing instances and communities: https://lemmyverse.net/

Not too late at all. To change instances however, ypu need to register on that instance and do a new account. There isn’t a way to switch instances on one account. Many are hoping there will be at one point a functionality to export stuff from one account to another but I have no idea how realistic that is.