Use two finger or one finger for tapping? I still suck using two finger to match the rhythm, but I've seen streams where they use one finger on 5* map.. I'm wondering if using one finger is also kind of a practice to increase stamina/? ??
Are you referring to singletapping vs alternating?
Single tapping makes it easier to get high acc and be more consistent at the expense of building stamina much slower. Alternating sacrifices pattern-reading ability but it return unlocks essentially infinite stamina. Alternating is ridiculously hard to learn, and requires impeccable finger control, however.
Most players singletap because it's the easier style to pick up.