Teams Audio Conferencing - sharing numbers?

Stephen Bell I'm not sure what you are asking about when you refer to "sharing numbers". Up to 250 participants can join a meeting by phone (https://docs.microsoft.com/en-us/MicrosoftTeams/audio-conferencing-common-questions#how-many-total-phone-participants-can-i-have-in-meetings). Every participant calls the same number and enters the conference code shown in the meeting invite. (You can have multiple conference bridge numbers to make it a local call for users in different locations, or to provide a toll-free number. Callers can also use any of Microsoft's shared conference bridge numbers, which can be accessed from the link in the meeting invitation.)

It doesn't really matter who sends out the invitation, but it would make the most sense for it to be the person who "chairs" the meeting most often. Rather than scheduling a new meeting every week, why not just make it a recurring meeting? 

You don't need to worry about "scheduling conflicts for the phone number" because this particular meeting will have a unique conference code. Even if someone else had another meeting scheduled at the same time using the same conference bridge number, their meeting would have a different conference code.