The Visitors (1972) uses the same real-life incident as
Casualties of War for the basis of its narrative but then combines it with
Straw Dogs as a fictionalized post-War confrontation. It stars James Woods, Patrick McVey, Steve Railsback, and Patricia Joyce and was the second-to-last film of director Elia Kazan. It is an interesting double feature with DePalma’s visceral, gory telling of the infamous Incident on Hill 192.
*now I see you already had The Visitors on your watchlist
Dead Presidents (1995) is the Hughes Brothers stylized tale of a few kids from The Bronx who become Marines during the Vietnam War but find few opportunities when they return home to the States, resulting in them turning to crime including an armored car heist. Starring Larenz Tate, Keith David, Chris Tucker, Bokeem Woodbine, N'Bushe Wright, Freddy Rodriguez, and Terrence Howard. A sort of mix between
Carlito’s Way and
The Deer Hunter by way of
Shaft.

Since you have asked for fictionalized narratives leaning towards the exploitation side check out
Off Limits (1988). Willem Dafoe and Gregory Hines play two U.S. military policemen working in wartime Saigon trying to solve the mystery of what appears to be a high ranking officer who is murdering prostitutes. Fred Ward, Scott Glenn, Keith David, Richard Brooks, and David Alan Grier round out the cast. Not especially compelling as a procedural Who-Done-It but is a really strong group of actors and an interesting, sweaty portrayal of the era.

You have
Coming Home and
Born on the Fourth of July on your list but two more narratives with Vietnam veterans dealing with the pain, loss, and PTSD of the war are
Jacknife (1989) and
In Country (1989).
Jacknife stars Robert DeNiro and Ed Harris as two vets who are handling the trauma very differently with Kathy Baker as Harris' sister and a potential love interest for the spirited Miggs played by DeNiro.
In Country was the first major narrative to film at the Vietnam Veterans Memorial in Washington, D.C. The climax takes place there. Emily Lloyd plays the daughter of a soldier who was killed in the war, who died before she was born. Bruce Willis is the man's brother, a vet who is nearly crippled by PTSD. The cast also includes Joan Allen, John Terry, Kevin Anderson, and Judith Ivey.

While on the subject of that powerful wall, check out
Maya Lin: A Clear Strong Vision (1994), a documentary about the artist who was a 21-year-old undergraduate student when her design for the Vietnam Veterans Memorial was chosen. It covers some of the controversies around the wall as well as the power of it.

The Vietnam War spilled across the neighboring borders of Laos and Cambodia which to my mind makes
The Killing Fields (1984) fair game for such a list. Based on a true story it begins in 1973 while the war is still raging and follows
New York Times journalist Sydney Schanberg (Sam Waterston) and Cambodian translator and journalist Dith Pran (Haing S. Ngor) as they try to cover some of that spillage over the border. As the War ends and the United States pulls out of the region it leaves Cambodia to Pol Pot and the Khmer Rouge who perpetrated a genocide on their own people. The second half of the film follows Pran as he tries to survive and escape while Shanberg tries to search for him from the outside. Haing Ngor's real-life experiences were similar to Pran's, lending another layer of reality to the narrative. John Malkovich and Julian Sands are also in the cast as journalists in Cambodia.

If you groove to that one also check out
Swimming to Cambodia (1987), a filmed version of Spalding Gray's most famous monologue. Gray was an actor in
The Killing Fields playing a relatively small role of a U.S. Ambassador's aide and the monologue tells about some of his experiences on and off the set in Thailand where the movie was made. In Spalding's inimitable style his thoughts and stories drift far and wide (I absolutely love him!) and does include a powerful and digestible sort of history lesson on Cambodia and the Vietnam War.