Learned this speedrun and learned from other videos that there was an extra warp not in the current TAS.
I think Level 1 difficulty would be faster since you can get 10 fish and in the shop right away.
My idea would be get the 10 fish and go in the shop right away to win at the slots. You need to win 30 (so triple cherry to win 40?) to afford the gun (for the bosses) and the Green shoes, for max running speed.
And then you technically only need to get 2 maps, for the bosses to show up in 12 and 24. No other powerups make you go faster, you are just stuck with shorter, fixed jumps.
Taking warps doesn't refill time, so you need to collect Green hearts as you are warping to add time.
So it would basically follow the same route as my run, but getting Green shoes at the start, and not buying Hat and Feather in 15, and going faster with max speed.
1 - Gun, Green Shoes, Warp
6 - Warp
9 - Warp
12 - Santa Map
13 - Warp
15 - Warp
18 - Buy Map for 21 fish
21 - Secret Warp (this is the one the TAS doesn't take, maybe there isn't one in that difficulty?)
24 - End
The warp might be there on Level 2 difficulty, looking at it there is a shop hole at the spot, if that is Santa it would probably work. But the warp is at the start of 21, so skips 21, 22, and 23, so could make this under 10 mins, not sure exactly.
RTA run -
https://www.youtube.com/watch?v=lXCl1L2bBZE