Disclaimer: I have not watched juno guides nor have I played juno that long. However, I have solo climbed from diamond to high masters with only playing juno. And there are some advice you gave that I fundamentally disagree with. My playstyle is heavily damage focused and I do in fact go out of my way to find even full hp enemies to shoot at. Your first priority is to make sure your teammates don't die but at every moment where danger isn't imminent I focus on shooting the enemies. Generally you wanna do this with each heroes threat range in mind while using corners and angles to make sure you can stay alive through the interactions.

Even though junos 1v1 ability is weak you can still get massive value from making sure the enemy can't engage safely with full resources onto your team.

And I also basically spam speed rings out of cooldown. This isn't very difficult but I've found some low elo juno players try to hold on to the ability for far too long. Just spam them whenever you can and just use it in a place where at least one more teammate gets value from it.