Furball: 1 20 mm cannon, 75% fuel. This is best suited for furballing because of weight.
Attack: 1 20 OR 30 mm cannon, 500 kg bomb, 2 gondies, choice of fuel. Best attack loadout right there.
Buff Huntin: 1 30 mm cannon, 2 gondies, 100% fuel and DT.
Advantages to G-14 over K-4 are: Firepower, Turn Radius, and Ord loadout.
Same between both planes: Survivabilty (I think), and Roll rate.
Disadvantages to G-14 from the K-4 are: Climb Rate, E retention, speed over 15 k.
Best way to fly it: BnZ isn't a good style for the G14, in my opinion. Best used as a turnfighter, and try to keep your E as much as possible, although it isn't a terrible aircraft in the slow speed turnfight. Coming into a furball with a little altitude wouldn't be bad either.
Then again, G-2, in my own opinion, is by far best 109 in the game...
Hope this helps
Regards,
Subway