There were some very good units. By upbringing I am not normally taken to parachutists, but the Vietnamese Parachute division I knew were very decent people. It was to be effectively destroyed as a fighting force later at Quang Tri. The Marines were I believe good fighters but of somewhat questionable character and said to be loyal to Nguyen Cao Khi. Frankly I avoided their company, I found them very dangerous. They were also destroyed at Quang Tri. There were good Ranger Units. Montagnards as I call the Ethnic hill tribes were used by both sides as so much cannon fodder. The Vietnamese called them Moï.
The regular army had been trained to fight a conventional war; the Viet Cong fought a guerrilla war. They were originally armed with Garand M1, which I have said is a superb rifle, but the wrong one for the Vietnamese and the conditions of that war. They would later use the US M16.
They were also beset by political intrigue and corruption. I believe a brigadier general was paid less than a US army corporal. If I remember in the time of the French the lowest paid French public functionary had to be paid more than the highest paid Vietnamese, no matter if the Vietnamese had a doctorate and the Frenchman was barely literate. This was somewhat redressed during the latter part of the French rule but far too late.
There were also Regional Forces, which operated as a sort of militia in their own provinces. The Popular Forces, who guarded the villages and hamlets, and a Peoples Self Defence Force in the towns, much like a Home Guard, and probably more dangerous to the people they were guarding than the enemy. There was a form of Gendarmerie whom I always found decent. Also the civil police about whom I have spoken.
There was a small navy about which I knew very little.
The Air Force was very Gung Ho. I might deal with their commander, Nguyen Cao Khi, later. One cannot write a story about the war without him entering it. The pilots mostly flew A1E Skyraiders. A prop driven fighter plane used in close air support. Very courageous, a pilot's life was not worth much if he fell into enemy hands. We had a Skyraider clip its wings on our antennae whilst doing a victory roll over the camp. The antennae was 300 feet high.
Another nearly overshot the runway whilst landing at Phan Thiet, which was on a cliff, and then out popped his whole family of about six people.