I haven’t dealt with antibiotics for MAC, but from reading the posts here know that an infectious disease doc, preferably one quite familiar with MAC, is best for determining AB treatment. It’s good you have one scheduled.

Welcome to the forum, though I’m sorry you need to be here. It’s a great resource and many here have dealt with Mac for quite a long time. I believe they’ll be posting advice soon.

Airway clearance is a basic mainstay for bronchiectasis and many of us use hypertonic saline of 3-7% It’s available on Amazon, but some insurances cover. My pulmonologist says it’s like flossing-good preventive practice. I don’t produce sputum and do daily clearance. Those who produce sputum do it twice daily. You didn’t say if you use an Aerobika or acapella device. One of those after nebbing can help. Exercise is also helpful.
Take care. You are taking the correct steps to learn more about how to managing bronchiectasis.