Yah, it is WW2 craft and there are no supersonic effects, etc. but you can go fast without glitches. I have tried the korean war mod, and in a dive i've gotten about 1200mph. In regards to oppponents...they probably don't have guided missiles for it so missile interceptors like the F104 don't really stand a chance(the game is based around dogfihting). Though there is one website "Avhistory"??(i think) that has a series of weapons packs for various mods and downloads such as extremely large bombers. I remember it was required for an A-10 (which i didn't get to work) and one of them might include missiles of some sort.
I don't know about a lot of flight sims. I have only owned microsoft ones and they didn't have the F-84 in it( it was a cool plane). But if you want to see if it's a mod...just look up CFS3 mods on google. Sim-outhouse has been my number one resource.