-what is the current population level for North America players?-what is the current situation and level of activity for guilds?
Population is low, personally I like a small community, would I like more players around? certainly, however still very playable as is.
-are characters stuck in one server or can they move freely between servers?
They are stuck yes, however server merges are suppose to happen this month causing Artemis/Reni to merge, and the other servers to merge into Govinda.
-is the game pay to win? or pay for perks?
"pay for massive perks" I'd say pay to win, however it is not true, many people who play can pay all they want and still get crushed because they have no skill. Most of the top players now a days are all free to play, just getting to that level is the current problem, once there it is pretty easy. So if you are willing to put in the work to compete, it be simply be a "pay for perks game".