u/Born-Performance4300

Say I hit one string, say downward. Should I aim only downward, parallel to the fretboard, or should I also aim a bit outward? Where should my stroke end in term of distance from the guitar? above the string's plane?

For context, when I alternate between two strings at 'high' speed, I sometimes hit one of them twice accidently, I'm trying to understand what I'm doing wrong.

Also, will the answer change if I need to hit two strings in one stroke?