Letter of Recs from health related activities

Hi,
So I am planning on applying to many BS/MD programs. A few of the programs require an additional letter of rec from someone associated with a medicine related extracurricular. For the other programs, would it be a good idea to also include this letter? Specifically, I am applying to Rochester, Case Western, Brown, Temple, Upitt, and UAlabama.
Also, if the school uses common app, should I invite the person through common app or prepare envelopes to mail to the school?
Thank you so much!

@shiftydraw It is good to get the reco from non-school contact if that reco is going to be good. Since the whole process of applying to colleges and BS/MD program is so complex, try to simplify whatever is possible. So absolutely invite that person to the common app platform so that s/he does not have to send multiple times and it will simplify. But some of the program, especially the BS/MD office/app expects still in age old way, postal mail or separate portal to submit etc., So there you need to explicitly request that person to submit in the portal (eg NW or postal like UPitt or Temple). But make sure to give them stamped envelope with the address written. Also manage and read the expectation of your teacher or non-school person, if they are ok to do multiple times or they prefer only once. That will help you to decide whom you plan to use for which college and which program etc.,

thank you so much for your reply! also if I were to invite the physician through common app, would he be required to fill out all those questions as well? about the top % student stuff etc? I feel like sending letters directly would be better in this case to avoid all that