First off, against kirby i would avoid dream land and draculas castle, since kirby can survive anything if he doesnt get ko'd off the side. A smaller stage would take away that advantage.A few weeks ago, i lost to a kirby on dream land game 2, and I 3 stocked him game game 3 on FD. I like medium sized stages like smashville, pokemon stadium 2, battlefield, and also FD. Its easier to space out kirby on those stages, use your superior range and running speed to bait and punish, similar to how fox plays(campy yet approaching often at the same time)
Small stages are ok too, but that makes it easier for kirby to kill with an aerial, which is why i like medium-large ones except dream and draculas
Against charizard, I like the same 4 stages listed above, except i wouldnt mind DL and dracs because its easier to land kill moves on zard.
green hill zone is also good vs zard, its like a mini FD in some ways which is good for DK in that matchup. I dont like platforms against charizard because he can air camp and hit u through platform with nair