I agree with a lot of what he’s saying - although I think “light” is relative here. I never pick so light that I can’t here my strings snapping a little bit. I think it’s way more important that the pick attack stay consistent than that it be super light. I can pick pretty fast with a really hard attack - for example:
You hear string snapping through the alternate picked runs pretty clearly.
Wherever I tend to get tension in my playing, more often than not, I’ve noticed is when something is uneven about my picking. Such as, my upstroke vs downstroke is getting caught more in the strings, or when my angle of attack is changing a lot, such as if I’m doing a long run across several strings without making adjustments that keep the pick angle even. This is when you get into maybe thinking about messing with some helper motions on top of your basic picking mechanic.
Little changes like the angle of attack causing more resistance or the string gauges changing can throw things off and make me tense up. I’ve been going back and practicing a fair amount on one string runs on each string and trying to pay attention to - is more tension happening when switching between certain strings? And is my angle of attack to blame because I need to be making some helper motion to smooth it out? Do upstrokes or downstrokes tend to be less smooth than one another on a given string or in general? Really just trying to focus on getting the picking motion to feel smooth on each string, then working in string changes.
A big factor also, is those one string runs help focus on hand synchronization, and take the string changing variable out of the equation. That’s helped me clean up things a lot, and getting in sync also seemed to help my speed - I think I’d subconsciously know I’m a bit out of sync and not want to push faster without realizing the root cause - it wasn’t speed that was holding me back but the hand synchronization was just off enough to throw me off. Maybe even something very minute like hitting a string when it’s not properly fretted yet was making the picking feel uneven and causing tension that way.
That said, when I first started playing I got ahold of one of the Stylus picks and practiced getting control over pick depth a fair amount. I think it was of kind of limited use, but it was so far back it’s difficult to know. Also I think pick depth is a bit relative - one you have a lot of control in terms of finding your comfortable pickslant and angle of attack, you can make very tiny variations in it and really change how much you’re snapping the string even with a pretty shallow pick depth if you have a flat angle of attack.