If you will need to identify the TEIs at any later point after registration then it should be a tracker program because the event program will not identify the TEI for you.
Since you are starting a new, Capture app is recommended. Note that the docs mention that “the Capture app serves as a replacement for the Event Capture app. In the future, the Tracker Capture app and the Data Entry app will also be incorporated into the Capture app.”
I think this is similar to a question posted before in another post and has been answered by @Enzo:
Yes! As long as all the programs have the same tracked entity type (‘person’.)
One recommendation is to check out Tracker Use Academy as well as Tracker Configuration Academy both of which cover all your questions and more (maybe not the details behind the SMS configuration but that can be found in the documentation – see link posted above by Enzo). It’s recommended to join live and there will be academies coming soon (Academy Schedule - DHIS2) but you can watch the recordings for now.
You can also review the docs here Tracking individual level data and feel free to keep posting with your questions and remarks.
Thank you!