There's tons of MiG-21F overlap with the F-4E, but actually more so with F-4B, C and D. The bis is sort of a choice without a home, unless you would still want to go ahead and place the bis in the same arena as F-15s and the like. If you want to dogfight in the most likely of times and places, then the MiG-21F is your best choice. Then there's all the J-7 and F-7 variants, many of which but not most are nearly identical to the MiG-21F. The PF and PFM are okay, but have too many compromises for a sole focus in DCS - but if we are being aspirational, then a spread including the -F-13, -PF, and -PFM are what we need to cover the most active times where the MiG performed its intended role. To me, I'm not looking forward to placing the bis on the Afghanistan map, and the Afg map seems like a total fool's errand for the series; bomb huts in an Su-25 or do unending orbits in an A-10. No thanks.
PS the MF is an awesome beast, and would have been a better choice than the bis.