Tricia, hope this is of some help.
Most of the time you need comfortable clothing to cope with a range of conditions. Most of the time when I went it was warm to hot, especially in Southern Vietnam and Cambodia. Also took some smart casual clothes for some of the evenings.
As far as malaria protection, you are right, some took Malarone or alternative, some used 50% DEET. My surgery advised that anti-malaria drugs were not totally necessary and so I used 50%DEET from Hoi An onwards.
Hope you enjoy it as it is a great trip.
John