Planning a last minute trip to Vietnam-

What is the most luxurious, least-touristy, least unpleasant way to experience Halong bay? Which boat? Which activities on the bay? Is it worth staying overnight or better to just see it above from a helicopter?

I am trying to determine if a trip to Halong bay is worth dedicating 2 nights of a trip to, one in Hanoi when we land from USA so we have a fresh start in morning for the Halong bay and then one night on a boat on the bay. Or, if we should just skip this whole area and spend the nights at Amanoi.

Thanks in advance!