I both wargame and RolePlay. T2K is a great game to crossover the hobby since building and modeling the wargaming components requires a small number of unique vehicles instead of a Battalion of 58 identical vehicles.
I'd recommend 20mm and 1/72 troops and 1/72 – 1/76, and even 1/87 scale vehicles are excellent for T2K.
Plastic figures are very convertable, or you can use a huge range of figures. In 1/72 the old Esci US Vietnam and NVA boxes as well as the Warsaw Pact troops make great figures. As do many HO scale civilians. You can easily do 'paint' conversions and a NVA figure with an AK-47 becomes a resistance fighter wearing blue jeans, hiking boots, and a flannel shirt…
As for vehicles, I think the larger scales work very well as they are fun to customize to reflect the ad-hoc nature of T2K. Toy Cars: "Matchbox type" also offer great ability to field commercial trucks, pickups, "technicals" and even bulldozers. I've converted two with plastictuct armor plating to represent expeident armored vehicles.
1/72 figures are commonly available at hobby stores or online. The below link is great to see what you are buying online.
http://www.plasticsoldierreview.com