Different inputs loan themselves to different hand movements, especially the left thumb. This has consequences for your tech skill because doing one input is going to have a bearing on the subsequent input. Though it’s most noticeable on the joystick, it’s also a factor on the right hand. Opting to use Z, L, tap jump, and even claw in certain situations can help mitigate flubs from hand position changes, making some techs and input sequences way easier, such as first frame aerials.
It’s important not to practice things in a vacuum. Just because you can do two different techniques consistently does not mean you can reliably chain them together quickly. For example, turn around up tilt out of stand, out of wavedash, and after an aerial are all significantly different inputs. Going from 8 o’clock to 1 o’clock on the joystick is not the same as going from neutral to 1 o’clock or from 6 o’clock to 1 o’clock. And in this case, all three scenarios also have different amounts of lag. Standing is lagless, and wavedashing has 10 frames of lag, but after an aerial, you can quickly adjust your stick to a position that would normally register as a jump without a jump coming out, which makes turn around up tilt much easier.
This is more commonly discussed, but I’d be remiss if I didn’t mention that there’s an asymmetry to inputs. Shield drops, ledge tech skill, moonwalks, cactuar dash, and many more techs are heavily controller dependent. Even snapback tends to have asymmetric influences on the stick. If your controller is perfect, doing something in one direction still doesn’t necessarily mean you can do it in the other. Given that your hand is on the left side of the joystick, you have to learn different motions to do the same tech in each direction. Having to pull your thumb to moonwalk to the left feels totally different from having to push it to do it to the right. Practice all your tech in both directions.
Posture when practicing alone is unlikely to be comparable to during tournament conditions. Whatever chair, desk, etc. you have at home is not going to be at the tournament. If you’re like me, then how hard you’re trying is going to be correlated to how much you’re leaning forward. You probably won’t have the same “Armada lean” when you’re fucking around in your room. Moreover, you won’t have sweaty hands from being nervous. Being able to do something in your room 1000/1000 times doesn’t mean you can do it under pressure. However, the reason for you performing something incorrectly in tournament may be something other than nerves. Practice is most effective when there is no disparity between practice conditions and tournament conditions. This is obviously not possible, but minimizing the differences, or at least being cognizant of them, will help you adapt more quickly to performing in tournament. Reflecting on recurring flubs and adjusting how you practice can sometimes lead to consistent performance even in pressure situations.