Unable to locate a settings in Teams client or web app on "Music on Hold" "User can control" in pic

If I am reading your question correctly, you are looking for this setting on your teams client. If that is the case, that is not where this setting is. It is in the teams admin portal. If you are a teams admin for your tenant, you should be able to get to it by going to https://admin.teams.microsoft.com/ . Once you are there, it is under the voice section and then calling policies.

Best,
bp