The third party MiG-21 should be excellent. Beczl had that model in Flaming Cliffs 2 for a while (as well as other excellent models such as a SCUD launcher). With official DCS support he should be make a first class product.
The Aerial War in Vietnam.
There is some discussion about which aircraft did what in Vietnam. Note also that even the F-105s cut up the MiGs (although MiG-17s, not 21s) a fair bit. After the initial MiG scares (which everyone harps on about, to the exclusion of later results) the MiG performance was actually not that good (once the USAF and USN changed their pilot training policies).
Here are some links to the actual kill records, for those that are interested in such things:
The US Air-to-Air victories in Vietnam. The same database holds the Vietnamese claims as well (nb. notice how the Vietnamese Air Force has very little activity in 1969 and 1970 - both the NVAF and Vietcong were on the ropes at that time).
http://www.acig.org/artman/publish/article_243.shtmlWikipedia also has an article, including operational (non-combat) losses. Most US losses were to ground fire:
https://en.wikipedia.org/wiki/Aircraft_losses_of_the_Vietnam_WarWikipedia article for F-4 has kills by weapon:
https://en.wikipedia.org/wiki/F-4