The main problem with creating your own groups on EP was the many duplicates and misspelled ones, but organizing them underneath the current categories solves that. It won't matter whether there are 2 or 100 similar ones if you can simply follow the category to follow every variation at once.
With that, I see no need for any limitations on amount or requirements, just moderation of hateful ones and other undesirable topics.
Groups added a layer of creativity and I would like to see that freedom back. As long as posts are in the right category, it should be allowed in the "wrong" group if that adds to a joke for example.