New to DCS: A Follow-Up

Hey all,

So I've been flying in DCS a fair bit lately. I can now start the Mustang without referring to notes, I'm reading up on Chuck's guide on it, and I feel relatively comfortable flying it. My question is, how do I know when I'm flying in sim mode vs. game mode? I want to make sure I'm not feeling all accomplished only to find I was doing easy mode.

Second of all, as the Mustang has no armaments, what can I be doing with it other than just flying? Are there missions I can still fly? Or should I dive in and buy a module so that I can do more? If I do buy a module, what would you recommend? I'm a WWII junkie, but I do think a jet would be a ball to fly. I primarily want to fly interceptors/fighters.