Does hitting the strings crosswise increase the speed?
I edited the post, in second video I slightly bended the wrist
Yes, pulling across the strings is faster. It's just a quick pull straight across. This keeps your fingers higher (they don't dive as deep between the strings so you dont have to adjust them as much).
When you get a pull on a sting straight through, it should land in the perfect position on the string under it ready to pluck.
We can give you a little guidance, but this is something you'll really have to figure out on your own. It's kinda similar to learning to slap. Everyone strikes the strings a little diffemet to get the sound they want. Finding the optimal angle to strike a string is a personal thing cause all out fingers are shaped differently.
For now just play. As you play more, you'll start to notice things that could be better. Just fix those issues as you notice them. This is something nobody can do for you. Somtiems fixing a plucking issue is just the tiniest adjust. Half a mm of finger tip less on a string changes its sound. It's really that sensitive.
I can give you generals. Like when playing motown, I use quite a bit of finger pad, but when playing Rock, I barely touch the strings with the tip of my fingers. Using just the tips adds brightness and attack to the sound where using more meat softens the attack and adds more bass.
I keep saying it , but it's true. You'll have to find what works for you and the sound you want to make. Our fingers can make a HUGE variety of different sounds. This is where rhe "tone is in the fingers" phrase comes from cause it's true. Even finger to finger on the same hand sounds different.
I could guide you to sound just like me, but that won't help you. Use this time for sonic discovery. When it comes to your sound, your plucking fingers are just as important as where you place them and eq. The can wildly change the sound in ways a lot of players dont fully understand.
My fingers can get rather close to a pick sound, but also a deep, dubby sound and lots of other sounds in-between.
So can yours. You just gotta figure out how. Callouses help fir a bighter , picked type sound. Soft , meaty tips sound more like motown.
I can't emphasize how important learning YOUR fingers is if you want to get the most from them
Also strings. Worn in steel strings can be blazing fast. They feel grippy at first, bit as skin oil builds up on them they get slick. Once that happens you can fly with the speed. They can feel almost too fast at times due to how easily your fingers glide over the strings. Steel can get slippier than coated strings sometimes. I have to wipe my down with a hot rag at times cause the get too fast for me after about a week.