New Zoom User - 2 VoIP - 7 Mobile Phone Users - Need Recommendations

Do the Mobile Phones have to have a Phone Number Associated with it or is the Extension sufficient enough?

Zoom account regardless of device use does not require a direct number assigned not unless you want the user to be directly called from external sources. If they need to call out though, they will need at-least a Zoom phone metered license and a caller ID ( can be company number , AR number, Call queue number).

Will the Mobile Users be able to call using the Zoom Mobile App and if so, will the company phone number (which will be ported) display in Caller ID? - Yes, Zoom admin can set the caller ID for the users to show the main company number.

Will I be able to add the Mobile Phone Users to a caller queue if VoIP calls don't get answer and then add Mobile Users in priority to who gets the call next and then so on even if they don't have a phone number just an extension, or do they need a phone number too?

Yes they can be added even if they only have extension, they will need at least a metered Zoom phone license though to be added to a call queue.