Best way to see Vietnam?

I’m trying to plan a relatively short trip to Vietnam from the UK which will be around 9 days/8 nights at the end of this month (v last minute). We’ve been to Vietnam before so have done Hanoi and some excursions from there but want to really maximise our time there and see more of Vietnam.

Ideally we’d be flying into Hanoi airport and travelling from there but any tips on the best way to maximise our time there and see Vietnam? Thinking maybe tours, trains or cruises around potentially but very open to ideas.

Thank you!