There was a big long thread on this subject a couple of years ago, if you can find it. Will summarize what I recall from memory ...
I don't believe this setting has any relation to date or region. WOFF sets up the number of enemy and friendly flights based on the historic period (squadrons in the area, battles going on) so you don't have to worry about that. RAI setting is there to allow you to 'throttle' the amount of activity to a level where your computer won't choke on too many aircraft flying at once. My understanding from old threads on the subject is that the Regional Air Activity basically sets the size of the radius around your location that WOFF puts activity into. Light activity creates a smaller zone of activity around you, while ultra heavy is closer to the whole front being active. OBD basically said to set it as high as your machine can handle, so keep upping it until you see your frame-rates struggling then back it off a bit and leave it there.
Last edited by 77_Scout; 06/30/19 08:31 PM.