This is kind of how it works (at least early game. I'm not sure if this counts as anything spoilers, but I am trying to avoid giving spoilers but rather just explaining basic controls and mechanics):
You can choose to stealth or brashly approach enemies. They have health bars and weakpoints. If you let them survive, they might alert a horde of more enemies (especially if they're watchers).
If you get caught in close combat, you can aim your bow to take out weakpoints for more damage, or at their general body for less damage. Or you can use R1 for spear attacks or R2 for stronger spear slashes (think the difference between Link's sword slash and his aerial jump). You can dash with circle, but there's no block or guard. You crouch with square to increase your stealth.
You can also strategize by using special weapons other than your bow and spear. These are bought by collecting valuable items.
If you get hit, your red HP bar goes down. You restore it with medicine (the green bar) which you gather from your surroundings. The red bar will restore equal to the depletion of the green bar, which is controlled by tapping up on the d-pad to heal.
It was quick to learn and so far it's satisfying. It's not very deep hand-to-hand combat (obviously, it's not Nioh or anything lol), but the depth of the gameplay itself comes from the options you have in taking out enemies.
This is just first few hours though. I have no idea how the combat might open up even more.