I have been trying to find out what the North Vietnamese would do to the Southern Vietnamese at the end of the Vietnam War. Everything I search for only talks about the PoWs, not the South Vietnamese.
This is one of those subjects that is easy to find information about if you know the terms to search for. Otherwise it can be a real pain in the derriere!
People like former South Vietnamese military officers, government workers and other supporters of the former government of South Vietnam were sent to "Re-education Camps" (According to the Wikipedia article, these were called "trại học tập cải tạo" in Vietnamese. As someone who doesn't speak Vietnamese, I'll just have to take their word for it).
There were at least 5 levels of these re-education camps, and they continued to operate until at least the mid-1980s. Those considered to be most 'dangerous' by the North Vietnamese were incarcerated in level 4 and level 5 camps.
In addition to Wikipedia, there are a quite a few sites that explain the system of re-education camps and describe the conditions within them. An example would be this page from vietnam.info.
I'm assuming that you truly are interested in this research so I will be forthright in my answer below.
First, I think it should be obvious why you cannot find information that satisfies your research hypothesis. The short answer is real historians normally do not drink the kool-aid of political ideology.
Second, this question assumes the generally accepted confrontation of North vs South Vietnam is correct. Cold War propaganda is how I will term it.
Viet Minh and Ho Chi Minh
Do not forget the origin of the Viet Minh, it was anti-imperialist and anti-colonialist, not anti-Viet. In 1976, Saigon (in South Vietnam) changed its name to Ho Chi Minh City. And who was Ho Chi Minh? The founder/creator of Democratic Republic of Vietnam (North Vietnam).
All of Vietnam celebrates Reunification Day (aka as Liberation Day), after they kicked out the US Army from Saigon.
The answer to your question(s) should be obvious if you think about these simple but crucial points for a moment without reference to accepted wisdom (whatever that means). In short, the question does not really make any sense from a Viet perspective.
Please allow me to say that my answer tries to address this in terms of history, not political values. I am not Viet and no, Vietnam today does not separate itself into South Vietnam vs North Vietnam. It is simply Vietnam.