The Microsoft Graph API doesn’t let you determine who the host or attendees of the meeting are dynamically. That’s why you should use Meeting policies to setup which groups of users are allowed to join or not.
By doing so, you can have the flexibility to create policies that represent your organisations needs. You can allow everyone to join the meeting, narrow the scope to only users from your domain, setup if they can skip the waiting room and join directly, etc.
For the full options Teams provides, refer to Microsoft’s policies overview documentation.