9 days in North Vietnam on at the end of April

I am an architect and cultures-urban photographer who is going to spend 9 days in northern Vietnam in the end of April. I have several questions:

1. Any recommendations for a route starting and finishing in Hanoi? I'm not into trekking or museums unless they are exceptionally outstanding.
2. Any recommendations for areas to stay in Hanoi? I'm looking for an interesting central area where lively activities take place both early in the morning and in the afternoon/night. Unique, beautiful hotels?
3. I heard that Ha Long Bay is super busy with tourists. Is there any unique way to see the bay without the hustling waves of tourists?
4. How would you recommend getting from one place to the other? I won't have a backpack but a large suitcase.
5. Any other recommendations for hidden gems in the area? Or tips that would make my experience there even more special?