JojoWiethoofdCoaching in CSGO is 'play calling' before/after rounds, there is no coach in spectate freecamming while also maincalling, which is imo how it should be for TF2. A coach can spectate it's own team and call how to approach the next mid, when to call a time-out etc. but no mid-round shot/play calling should be allowed (at least on LAN this can be enforced).
Pretty sure this can be enforced online using the plugin being discussed in this thread.
Not really, you can just stream your game either in discord or on a private twitch stream to the coach with a really small delay and they can still see everything mid round regardless of the plugin.