We could make a verification movie for max score by warping to world 8 then save and quit, then reload the game and get warp whistles, keep going until you have 27 warp whistles.
During the max score TAS, Complete every level in world 6 except the airship, then warp back to world 5, rinse and repeat.
Getting 27 warp whistles on the NES version requires a different method due to it not having a save feature.
It requires dying lots and lots times so that the levels can be repeated after a game over.
I recommend doing it with 2 players 'cause you don't need to repeat the first two levels.
Player 1 completes level 1, Player 2 dies in level 2, Player 1 completes level 2, Player 2 gets a warp whistle from level 3, Player 1 dies in level 4, Player 2 gets a warp whistle from the fortress, keep dying until you get a game over, Player 1 selects end, Player 2 selects continue.
The only downside is that you can't save, and despite said method in getting the warp whistles is quicker on 2 players, it's slower to get the max score on said mode; unless you use a save hack.
Without getting a game over, the most warp whistles you can get is 3, or 4 in the Famicom version thanks to a glitch.
Speaking of the Famicom version, you can do the rinse and repeat part indefinitely due to said glitch, and it's quicker than the NES version, but the enter level screen transition is a little slower.
The NewGame+ for the NES version gives you 28 P-Wings at start.
The GBA version is also unique. Get 2 warp whistles as usual. Is it possible to finish a level at exactly 000?
You have to beat the game just once in order to select any level as many times as you like.
If it's possible to beat a level with 000 left, then only do it with Mario for a NewGame+ verification movie.
For Mario, make it to the end without killing any enemies, getting any coins or power-ups, and breaking blocks.
1-1 Mario gets a flower panel with 000 left, 1-2 Luigi completes level after getting 80000 points, Card game Mario gets a flower, 1-3 Mario gets defeated by a Koopa Troopa, Luigi gets warp whistle, 1-4 Mario falls off, 1-Fortress Luigi gets warp whistle, 1-4 Mario falls off (again), Luigi uses warp whistles to get to world 8. 8-Tanks Luigi defeats a Boomerang Bro. to get a star. 8-Battleships Mario uses a flower before entering in order to defeat Boom-Boom while scoring no points, finish at 000. 8-Airship Luigi finishes the level, 8-1 Mario gets a flower panel with 000 remaining, 8-Hand Trap Luigi falls in lava, 8-2 Mario gets a flower panel with 000 left and gets a 3UP to bring the remaining lives from 2 back up to 5. 8-Fortress Luigi finishes the level, 8-Super Tank Mario completes level with 000 left, 8-Bowser's Castle Luigi defeats Bowser, game complete. Now get 35 warp whistles to start with for the max score TAS.
There is be another way to get max score, the e-Reader cards.
We'll never have too many unicorns.