I only just realized that holding Left + Right for 2 frames when Kirby has 0 speed results in an overall increase in distance traveled for a given number of frames, since the increase in acceleration outweighs Kirby's slight backwards movement for those 2 frames. This can be useful during the start of most rooms, after taking damage, or when changing direction, like in the last room before Whispy in level 1. In a lot of rooms it doesn't help since it's not enough to save a framerule, but it can also change when the game lags, so it can potentially save a frame or two that way. I redid what I had so far with this knowledge, starting with the framerule I had saved in the first room.
https://tasvideos.org/UserFiles/Info/638549003242406298
Hopefully I don't find anything else that causes me to redo the TAS from the start again.