A Grade 1 heart murmur is the lowest grade! My Raiden has a grade 3 which is in the middle. He had anesthesia when he had his teeth cleaned and all went well. The vets were not worried. It is true that some heart murmurs clear up by themselves, but it is not unusual for a bengal to continue with a heart murmur. Most live long, healthy lives with one as long as the grade isn't a 4 or 5 (or 6 in some cases). You can easily spend thousands of dollars to get more information on Miko's murmur. Is it worth it? For a grade 1, I would not worry about it, nor would I worry about the anesthesia. Your vet is the best source of information. Know that a neuter takes very little time (some vets have it down to just a few minutes).
As for the recovery -- you won't have to worry about stitches as they usually just use glue. It's much easier on a male cat than a female. They say to keep the cat quiet for a couple of days, but the one cat I had neutered would not settle down and was fine. He was an outdoor cat (stray) and he would not stay in the house. Once again, I think you're over worrying a little, Matt. But I love it! It shows just how much you love Miko.
I don't think a bengal's voice changes over time. But they do have like 100 different meows that they can do. Raiden has one that sounds raspy and he's fine. When it comes to observing cat behavior -- if they are eating, drinking and using the litter box okay (no diarrhea, constipation, vomiting, lethargic), they are okay!
You'll get the hang of bengal ownership in time, Matt!