Yeah, 50 + 15 sounds perfectly reasonable. Having 65 followers for a clanless player is quite comfortable, and 200 maximum is a much more reasonable cap than 100, without going too high.
I would also be okay with 0 + 30, which would eliminate the disincentive to clanning. True, 300 sounds high, but I haven’t seen many 10-player clans on PVE-C servers. And although 30 sounds like it’s not much, it should be enough per player.