Those two groups live near the territories of the clans, kittypets are NOT seen by the average clan cat. But it doesn't mean that the cats aren't aware of their existence. Cats like Aspenflight, Foxpaw, Rosanne, Rosanne's kits and few more others that were kittypets or had kittypet blood.
Other clanless cats are the cats of the Street cat Organization, but these cats live far away from the clans, they chose to live a different life, in different circumstances. But again, there are street cats in the clans that joined when the clan seeded them the most.