Option 1 - Create a membership associated only with a member.
You can the associate the membership with a team as well.
Option 2 - Create a membership associated only with a team.
You can the associate the membership with a member as well.
You should use the "isPersonal" parameter only when assigning a membership to a member, who's part of a company, i.e. when you're filling out both a member-id and a team-id and also if that member is going to be personally be billed for it.
If a membership is going to be associated with a member only, it doesn't need to have the "isPersonal" parameter enabled as it's assigned to them alone anyway.