In-app purchase or 3rd party payment?

I would be grateful if you could give me an opinion on an app I am developing and if it would need to integrate In-App Purchase or 3rd party payments e.g. stripe or paypal.

Patients use the app to book a consultation and have a live video consultation within the app. The doctors will connect with the patient via a website link and would not be using an app. 
There will be other charges depending on the outcome of the consultation such as for prescriptions and letters. 

I have read comments from previous questions raised by developers but I am still confused as to if live consultations mean that in-app purchases would not be permitted. I cannot see any information on the developer's guidelines about this. Furthermore do prescriptions and letters count as 'physical' products even though they are sent by email to the patient?

Many thanks in advance for your help.

Ps this was posted in the in-app payment section previously but I don't seem to be receiving any views!
In-app purchase or 3rd party payment?
 
 
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