Hi @amyfaith and welcome to the family. As you have already discovered, this place is a gold mine of support. (Debra's the best!!) I've posted here several times about my experience with Camzyos (life-changingly-positive with no side effects), but I'll try to speak to your COE question. I'm in Canada where I think we might have the equivalent of a COE but it's a 3-4 day drive or a 7 hour-each-way, $700 return flight. My options were limited. I fought for years looking for a diagnosis but fortunately, as soon as my local cardiologist saw textbook-oHCM all across my test results, he recommended Camzyos. I had nothing to lose by trying it (black box warning comments to follow). Had he NOT recommended it (and had I even known about it), I probably would have dug deeper and looked for second or third opinions. I also have every confidence that he would have helped me with options if Camzyos had not worked. Not everyone is so lucky with their medical care. If you are confident that you are getting good care, and your second opinion agrees with the first, and your specialist at University of Vermont supports that too, and all suggest a treatment plan you are comfortable with - sooner or later you will have to trust your gut. Learn everything you can, and don't be afraid to look farther afield (like a COE if you can access one) if you have doubts. There is a Camzyos web site that has excellent information that explains how the medication works.
About the black box warning, the way I looked at it is that oHCM is effectively (perhaps not strictly accurate, I'm no expert) a form of heart failure. If Camzyos MIGHT cause heart failure (which is not the same as a heart attack), I'm probably not much further behind. Also, while on Camzyos, I would be closely monitored for months/years, so changes or deterioration in my heart health would be detected much earlier.
All that said, I'm not a doctor and have no medical expertise, so do not take anything I said as medical advise. It's just my own experience with oHCM and Camzyos. Everyone will walk a different path. Surgery, ablation, medication,... stay positive - there are options. And keep in touch with the good folks here at the forum. We will all want to hear how you are doing and wish you a quick return to health!