Hi @Kalie,
All of your requirements are possible.
- Can be scheduled ahead of time on the calendar: You can Open Calendar from Teams application and select New Meeting. Select the desired time of the meeting
- Can have internal and external attendees: Two ways to add external candidates. Add their email in attendees field. They will get email notification. If you add them as a contact in your exchange environment, you can search their email from the field and can automatically filled. Internal candidates names can be selected from contacts list
- ALL attendees can dial in with video, not just audio: By default, notifications sent are allowing video+audio felicities
- Can be scheduled by an admin, aka someone who is not attending the meeting: Ensure that you have delegate access for the calendar of the person. Signed in to both Teams and Outlook. Open the person's calendar that you manage. Click the day you wish to schedule the message for and click the “New Teams Meeting” button on the Outlook toolbar. Follow the same procedure
Please mark as "Accept the answer" if the above steps helps you. Others with similar issues can also follow the solution as per your suggestion
Regards,
Manu