They certainly look ready to be pricked out into individual pots. Lift up a clump and gently pull the individual plants apart and replant each in its own pot. Or discard some if you don't need that many.

Without knowing where you live it is hard to know what to tell you to do next. In a mild climate they could go outdoors or into an unheated glasshouse after they have settled into their pots. Catnip is pretty hardy. But if you have cold winters they probably need to stay inside in a cool place with plenty of light.

Agreed. Unless you live some where warm year round, you're going to want to over winter inside. And much of the US is far too cold now to even try to get pampered houseplants hardened off and planted outdoors to go dormant for the winter.

If you're plants were outside, I wouldn't worry about thick clumps much because catnip grows that way with the strongest plants dominating. But since your plants are going to have to remain indoors for the winter, definitely do as flora suggests and separate.

FataMorgana