Slide guitar use a slide, and you tune the guitar differently. I've almost
never used picks. I just use my nails...Check out the claw technique. Mark Knoffler is a fantastic finger picker. Try playing Landslide by Fleetwood Mac to get started on picking. Picking is most often repeating patterns. Your thumb essentially plucks the bass line.While the fingers do a pattern.
I don't know about the Hawaiian roots of the steel guitar. I would think it came from the south/mississippi/blues. Guitars have a really cool history going back to stringed instruments in Africa. So a lot of the slaves brought a style with them which helped create blues/jazzz and such. They also made "guitars" out of whatever materials they could find.
My favorite slide guitarist is Duane Allman..But I love blues-hence the username, and jazz. If you haven't already, check out Derek Trucks and/or Tedeschi trucks