Welcome to Maine, in advance!
You will get lots of help here. Pick up Rod Gervais' book.
In general I would opt for a peaked ceiling, both because it can eliminate flutter echo and also it will increase the volume of the room. However you will need to be aware of where the reflected sound is aimed, and treat it accordingly. See this article for more detail on managing early reflections: RealTraps - Creating a Reflection-Free Zone
Don't be afraid of drywall, with enough treatment it will be fine. You won't find a more cost-effective form of mass to add to your walls for soundproofing.