Yeah, the whole large realm thing doesn't work out well for the rest of the island's players.
It's really hard to predict, I don't think there are hard rules of how realms of a certain size will influence global politics.
Realms being too small can also hinder warfare by their inability to conquer cities. And there's always the "why take more regions, we already don't have enough nobles for all of our regions", which is worse in realms with few players.
Behemoths can snuff out conflict... but they also have the means to spark them, unlike micro states who cannot snuff out conflict, but do not really have the means to spark them. The HD vs Morek conflict can only escalate as much as the bigger nations want it to.
