Seems like you're experiencing some frustration...
I have been playing for about 2 years now and for first year+ I sucked big time. I didn't understand why I was getting wasted all the time either. My first realization was that I needed to get a joystick instead of mouse, big improvement. Next came my realizations about altitude and patience (in other words not going for the first con I see, but climbing out and circling around getting a good advantage point on my foes). The third realization was what weapons are most effective. If you fly a lot of different planes, you will soon find that some planes simply knock the socks off other ones. This is due to the variety of planes available and the eras they come from (I'll explain a little bit later).
First, to answer your questions about tanks, AP is armor piercing, HE is high explosive, and Smoke is just that. Use backspace to change between these rounds as necessary in the #2 main gun position. Smoke can be effecttive when approaching an enemy tank base, as it clouds nme tanks view of you. Armor Piercing is good for knocking out important stuff on nme tanks, and high explosive are good for buildings. I prefer the combination when attacking an nme base, since you might need to kill tanks and town buildings. However when going for a vehicle base, I choose armor piercing to rack up those tank kills.
Now on to airplane ordinance and convergence settings. In the hangar, you will notice a tab at the top of the clipboard that says Set Convergence. These settings allow you to set how far ahead of your airplane the bullets meet. You need to know a little about the weapons characteristics in order to determine this. In general most Cannon are slower and have less effective range than the Machine Guns. This is not always true though. For example, the .303's on the Spit I, V, IX, XIV, and Hurri I are only effective out to about 300 yards (maybe 325). After that they lose punch and it will be extremely hard to down a plane with just those. However the Hispano cannon on your Spit will do a number on that nme at greater range (to about 400-500). On a lot of planes though, the general rule of thumb is cannon are slower. On my FW 190 A8, I don't use cannon farther than 400 yards, only my MG's, that way I save the cannon for that all unforgiving 300 yard shot which in a small burst will leave someone spiraling to the ground. On the American planes, with the .50 cals, those bullets tend to have better trajectory than most other planes, so i set the convergence of my P51 and P47's to be about 400-500. I know they will still be effective at that range, and the US used them because of reliability of flight path and punch.
Late war airplanes tend to have better weaponry as well. Ever notice how those 262's and N1k's just keep blasting you to smithereens at absurd ranges and lightning speed? I STILL have problems when people in N1k's can down me from 900-1.2k range. The reason they are more effective with those 20 mils, than say a Hurri C is the fact that in real life, the plane was made later in the war and had better weaponry. Aces High does a fine job of making the planes in here represent accurate real life data. Don't be discouraged though when those N1k's down you in your 190 A-8 model though, because his ENY is only 10 whereas yours is 35. You can get the official meaning of these values from the AH site, but basically divide your value by his and you get that many perks. So in this case, he kills you he gets about 0.35 perks, but you kill him and you're getting somewhere in the neighborhood of 3-3.5 perks. The perks also depend on many other factors which complicate the scoring, but don't worry too much about that.
I hope I'm not just telling you stuff you already know, but if you learned something from this post, then that's good. Read a lot about the weapons and plane abilities on this Bulletin Board, I know there are many people far more knowledgable about the planes, and would be more than willing to share that knowledge. Happy hunting, and any questions on specific planes, feel free to ask. I can give you some opinion and direction.
Jason
