They're random but based on a template. So while things are never exactly the same and you can't memorize things in an attempt to get by like a scripted mission, every bomber intercept mission is generally the same in that you fly to target location and engage bombers and escorts. Usually on egress you will run into friendlies and enemies mixing it up unrelated to your mission, which you can either engage with or just run past if you are damaged/winchester. It's the same old story--scripted missions are involved and interesting, but become dull to replay because they're always the same, while the random missions are always different but never THAT different.
Also, Pat Wilson made a CG like he did for RoF that is more complex at the cost of needing a better PC to handle the missions it makes. If you've used it for ROF you know what to expect there.
As for DCS, yeah, you can fly a WWII plane on the Black Sea map...but I can't bear to do it. Outside a pure A2A mission dogfighting, as soon as you get close to the ground you're reminded you've pulled a Final Countdown and are fighting the Axis in the 1990s or something.
Bottom line--if you want to fly say an A-10 or Mirage 2000 in a modern day map, it costs you the price of that module (whatever it is at the time) and that's it. The map, assets, and full roster of appropriate aircraft are included.
If you want to fly a P-51 or Fw190 in WWII, it costs you the plane, the map, and the assets. Only the planes to populate the world are free, but there aren't many of them right now so it's a bit anemic as you can't even fly bomber intercepts.
So, price of entry for "authentic" WWII experience in DCS is much higher than BoS or BoM even when they're not on sale and that only gets you ONE flyable. It may be modeled better, but IMO it's not modeled 8x better. That's why I don't recommend DCS for people looking for WWII flying right now, unless they have a group that flies coop that also has all the WWII stuff and has a DCS mission maker in it. Then they can be in a group that makes their own WWII missions and flies them together and THEN I think it would be worth paying the extra as that experience cannot be duplicated in BoS/M right now.
The Jedi Master