ED has recently promised 50% improvement in VR performance. Seeing how that goes will go a long way towards determining VR upgrade path.
Ideally, you want as good resolution as you can get. The Rift S ain’t it. HP is coming out with one that looks real promising.
All that lovely resolution is ruined if frames can’t keep up though. Thus the wait and see before being able to recommend anything.
One of the things I really love about DCS is the mixed era planes. You can play out all sorts of what if scenarios. The other day I was tooling around in a Spitfire and wanted to see if I could down a giant IL-78 (modern fuel tanker sized jet). Really interesting results. I could not bring that thing down for the life of me. It was pointed out to me to go for each engine. That was challenging but doable. What fun! Like taking down a boss.