Quoting romhacking.net: Super Bill Kill is a simultaneous 2-player version of Super Mario Bros. in which the second player can turn enemies into Bullet Bills and target them at Mario. This ROM was originally designed for an offline tournament at AGDQ 2019. You can watch the final match of the tournament to see the ROM hack in action.
Compared to the current WR warpless TAS, total 414 frames are saved in following levels:
1-3: 84 frames
3-2: 84 frames
5-1: 63 frames
5-2: 63 frames
5-3: 84 frames
8-2: 21 frames
8-4: 15 frames