There is less risk for clotting with Aflutter that with Afib. The irregular beats are more organized with Flutter vs Fib. Clotting is still an issue but not as great. I used aspirin for a couple of years with intermittent Aflutter but then mine became more frequent.
My first experience with Aflutter my HR was 300. After that I just had intermittent events with much lower HRs and with often self-converting. The more and longer you are in flutter the more stress it puts on your heart but the same can be said for Afib. Still I think knowing what I know now I would have used blood thinners. Ablations are much easier and more successful with Flutter than with Afib. My flutter ablation took 1 hour and was 100% successful since 2012. I just went through my 2nd Afib ablation 3 days ago as breakthrough Afib was becoming more frequent.
BUT you indicate your peptide level at 3300 is very high indicating that you heart is working hard. This is a red flag and means getting to a diagnosis and treatment possibly sooner rather than later is more important. I myself wouldn't go on a cruise with these peptide levels and I would be on blood thinners. You mention having a neurologist and bringing up Freidriechs ataxia. FA (or FS) Freidriechs syndrome both cause heart arrhythmias which complicates matters. You didn't say you have FA but you bring it up suggesting you are knowledgeable about it makes me wonder if you are being seen for it. But then you also mention Addisons disease so that is confusing.