Hello, and welcome to the need to make a hard decision. It sounds like you are on track to a diagnosis of your infection and its susceptibility to medications, which is what ID docs do.
Are you also being seen by a pulmonologist experienced in treating this infection who is regularly monitoring you lung condition - like whether you have nodules or cavities typical of MAC/MAI, and whether they are changing over time?
Here is a tip about how much experience the pulmonologist has in treating people like us - they will recommend daily airway clearance to help get the mucus out of our lungs, and perhaps offer an inhaler or nebulizer to help with the process, or a visit with a respiratory therapist. "The vest" is only one such tool, there are other options like a vibratory device.

Here is a current discussion that might help you - you can connect with some people who have decided to take antibiotics, and others who have decided to wait and watch.
https://connect.mayoclinic.org/discussion/should-i-take-big-3-inhaled-arikayce/
And here is an older, longer discussion by many people who were faced with the choice:
https://connect.mayoclinic.org/discussion/macntm-is-different-for-everyone-treatment-might-be-different-too/
Remember, based on the stage and severity of your infection, "watch and wait", combined with daily airway clearance, can be a suitable treatment plan for you.

Sue