Do moderators need to be members of the host instance?

Hey there. Like many of us I'm new to lemmy, and have also never really moderated anything before elsewhere. I'm thinking about starting a community here, but I don't really have the time or willpower to moderate a community if it starts to grow too much. It could be nice if there were others that wanted to help out down the line, but I'm unsure if they'll be able to if they don't have an account on this instance. Does anyone know?

My feeling is that it probably doesn't matter, but I'm unsure. Also, just out of curiosity, is it possible to make communities on other instances?