Hey there! It's no surprise it's frustrating - a lot of the combat mechanics aren't in place yet, and the resulting balance is pretty wonky, and there's some info that's missing in the UI.
Let me describe current state so you can get a sense of how it's working, how it will work, and where things are going awry (tl;dr somewhere in the middle):
The different stances themselves currently have a few effects beyond giving you access to different techniques - for instance, some stances ignore high, medium, or low attacks (prone ignores medium and high attacks, vaulting/flying ignores low attacks). Stances will mostly impact combat in those two ways - determining what techniques you have access to on a given turn, and the stance a technique leaves you in will, in part, determine the outcome of an enemy's technique. (ie - if I duck, and the enemy swings high, they'll miss).
What's missing: One of the key elements that's currently missing in this is the effect of perception on combat - which will allow you to get some information on things like enemy stamina and balance, but more importantly, what attacks an enemy is going to use in the future, including on the current turn. Another factor that's making this less effective is that context-specific attack modifiers - like an attack that deals critical damage when an enemy is on the ground or tries to dodge it or goes in for their own wild haymaker - are not currently implemented. Stamina and balance are also missing a few gameplay hooks that will make conserving them, trading them with the opponent, and punishing your opponent based on them a key gameplay aspect, so there's a large strategic element missing when it comes to stances.
The information about techniques is correct - it tells you exactly what that technique does. The reason you're seeing some unpredictable results, however, is because of a few hidden values that will be less hidden and more intuitive once they're fully implemented:
What's missing: So, you and the enemy both have an armor score. You'll occasionally see "It's an armor shattering blow! It reduces armor by X" - this is caused by powerful blows, or techniques that amplify armor destruction. This reduces the damage your attack will do. By far, though, the gameplay aspect that's probably causing 90% of your confusion is that as you or the enemy's stamina and health lower, your stats do as well. Meaning if you're near death, you're not nearly as strong as you would be at top shape, and you'll recover stamina more slowly. In the full game, this will not only be more obvious, but getting past an enemy's defenses and crippling them to prevent them from doing severe damage to you is going to be the primary focus of any successful strategy. Things like bleeding, actual armor and more complex battle effects like weapon disarming, counters and tripping not being currently implemented means this isn't quite ready yet either.
tl;dr - That probably is the source of your confusion - the gameplay elements which are currently not explained, visible on the UI, or fully fleshed out, like armor or stat loss as health and stamina decrease. We'll try to make things clearer and give more meaning to some of the idiosyncrasies with each new version, so hopefully it won't be frustrating forever. But to actually answer your question, here's a quick breakdown of the stances:
The three "core" stances are
Defensive - Balanced - Offensive
Switching between these stances is relatively simple and is intended to come with little penalty - except in the circumstances where you switch from Defensive to Offensive and vice versa. Around both Defensive and Offensive, there are a few related stances, not all of which every character will have, and which offer more strategic options. Most of these are not implemented yet, and so I'll talk about those at the end.
The other stances you've probably seen are Prone, Supine, Kneeling, Airborne, Blitz, and a number of erotic stances that will have their own techniques as well, but currently all have a pretty simple "try to break free or not" dichotomy in the available techniques. With the exception of Blitz, which is one of the stances I'll detail below, and is only available currently to Warriors in normal (non-story) mode, these are all positional stances, which mostly serve as transitions from one stance to another, and also provide some positional effects, like I mentioned earlier.
As for the complex stances which aren't in yet:
For Defensive, those are Stonewall, Counter, and Focus, which, respectively, offers a wide gamut of very defensive techniques, provides the means to perform specific counter attacks, and has techniques that focus (heh) on recovery, centering yourself, and preparing for more offensive maneuvers.
For Offensive, there's Blitz, Berserk, and Haymaker. Blitz is about a consistent offense meant to destabilize your opponent with fast, attacks, while keeping you agile and able to defend yourself, at the cost of being highly unstable, Berserk features techniques that are overwhelmingly strong, and similarly consistent, but forego any kind of defensive maneuvers and is difficult go get out of, and Haymaker is, effectively, a preparatory stance - once you're in it, you're committed to a large attack or nothing, and pretty much all Haymaker techniques take you out of the stance, so it's no good for consistent assaults like the other two stances.
Not every enemy but for some yes you can win against some enemies by just sex/seduction.
If you need help with combat follow this link (helped someone else with combat in it). https://itch.io/t/654969/need-a-solid-beginner-build-for-combat
