When your stamina partially depletes due to a move, it goes red and starts filling the red area with white. During that if you press R1 it will insta fill it.
Well, fill it at the point where you pressed R1. You could recover none of if you press right away or some to all of it depending on when you press R1 (or X/dodge in Low Stance). It starts stamina recovery at that point as well rather than if you don't press R1.
Noticed that dodging is also different in each stance with weapons active when you tap x twice or more. Low Stance you get dashes that can chain into each other, Mid Stance you can dash into a roll, High Stance is straight up rolling, weapon sheathed you get the Mid Stance dash into roll.
Attacking is also different (obviously). I pretty much only use Katana when I go into Low stance but you can keep attacking as long as you don't run out of stamina (if you do just recover it or let it fill back up). The Stamina Recovery with dashing is unique to Low Stance.
Mid stance you get up to four attacks but is a stance that is balanced between rushdown and high damage. Defensewise the best one for blocking and parrying.
High Stance you can attack up to three times, twice with basic attacks and a third time with a special triangle attack.
Each stance has a Combo Ender that can extend the combo by one attack but not necessarily one hit. In this demo the Katana has three finishers but the third can only be used in High Stance. You have to learn these special attacks but you start with Kick which you can use in Mid and Low Stance.
When an opponent runs out of stamina their bar glows red. Some enemies you have to knock down (mostly humans with heavy armor on) then followup with the finisher while unarmored enemies you can just use a finisher. Yokai and Bosses I can't figure out how to perform finishers on. Humans are tied to Mid Stance Triangle for Katana (twice for armored ones, you have to knock them on their ass first with a first triangle), I can't quite figure out Axes or Spears.
More or less I've been only using Katana, Axes and Spears are too slow for my preferred style of play.