Leaving next week and still unsure about when to take flights or use train and bus travel. We arrive Hanoi 3 September and leave HCM 20 Sep. Any suggestions welcome. We have about 4 days Hanoi-then will go to Halong Bay and have not decided finally on the rest.Prefer smaller places to big city.

Hue and Hoi An. You can get a flight to Da Nang and drive to both easily from there. I especially loved Hue. The royal tombs are wonderful, as is their smaller version of the Forbidden City. From Da Nang, you can fly to Saigon. I'm sure you can take overland transport but I can't comment on that since I flew between cities.

Thank you for super quick reply.
Also will we need jumpers,or raincoat or umbrella?????

November is not really rainy season there but in South East Asia, rain can come at any time so it's best to prepare for it and bring umbrellas. Also, it's always hot and humid so dress in light clothing that dries easily. Temps average in the mid to upper 80's F. I get the feeling you are from Australia so I apologize for not converting into Celsius!

Actually, in Hanoi it might be a bit chilly in November. The first time I was there, in December, I headed south early because it was cold and wet in Hanoi. Next year, apparently, it was quite warm in December. May depend on how early in November. Would suggest taking the train (likely to be full of Vietnamese) rather than the open-tour buses (likely to be full of backpackers sleeping off hangovers).

It was nice in early November last year in Hanoi. No need for an umbrella which I would have purchased in Hanoi if needed.

Anyway, OP is traveling in September.