Neutral Eggshot[]
When the egg controls are set to hasty, you can quickly tap and release A to do eggshots that will always have an identical angle every time. There is a 9 frame window, from pressing A to releasing it, for this to work. This is very useful because it allows certain difficult eggshots to be made consistent. By constrast, if egg controls are set to patient, there is a one frame window to do any eggshot with an identical angle. Because of this, for a category like 100% where consistent eggshots are incredibly important, it is highly recommended that you play on hasty.
Neutral egg usage in 2-3
An example of where neutral eggshots are useful:
Rising and Falling Neutral[]
Whether Yoshi is jumping or not influences egg trajectory, which can be see in neutral eggshots. Doing an egg shot then immediately jumping results in a lower angled shot (also works if you jump then almost immediately fire an egg as well, assuming you continue to hold down jump), whereas firing an eggshot while falling has the opposite effect: the egg angle will be higher.
The following gif demonstrates this concept with neutral eggshots. Watch where the eggs exit the screen on the right based on yoshi's jumping.
Upwards Eggshot[]
Upwards Eggshots
Straight up-shot: To do a completely vertical up-shot you have to stand still and: A) Tap A and hold up for less than 10 frames or B) Wait until your cursor is out before releasing A.
Angled up-shot: This happens when you make an up-shot by tapping A and holding up for longer than 10 frames, it's inevitable when running and shooting upwards. This also makes Yoshi face the opposite direction.