As far as I know I only calls (depending on your settings) and alarms will sound while DND is turned on. It would definitely make sense for urgent notifications—such as Ring—to still work though. It might be worth submitting feedback to Apple. www.apple.com/feedback
Doubt it. You can’t even receive message notification sounds on your excluded contacts with DND on, unless you have emergency bypass on. I feel Apple should really smarten up their DND to make it more app specific as well as allow multiple instances. Android is way ahead in this department.