Awhile ago I had IL2 -1946 with a few of the addons such as Pacific Fighters, Battle over Europe.
I want to get back into it and see that this game as progressed to some other level.

Where would be a good path to go to find out what is the most comprehensive route for the most single player missions in different theaters and time periods.

Would like everything from the Spanish Civil War right up to the most current air battles that IL2 can be modded to. (hopefully you don't need a computer engineering degree to install mods to that level).

Also I see there is BAT and SAS...are they compatible with one another, and if not which has the most to what I am looking for.

You want to use BAT that is hosted at SAS.
Once installed you can switch between different era's such as World at War being "normal" WW2 stuff and Jet Era to go Korea style mixed early jets and high performance props (what I am up last few weeks) and also WW1 style but I cant remember the name - easily switched between using that IL Selector that comes with BAT.

In my opinion, you get lots more gameplay in IL2 1946 and BAT over the current new titles (personally I've uninstalled the newer ones).

Jack 72,

Please read the install instructions, and once you up to running a clean Il2-BAT which is now up to BAT 3.7.1 then save it before modding your install.