The Nozomi (fastest Shinkansen) isn't but I think one of the others might........the Hikari maybe?
Yep, Hikari. Still really fast.

For us the JR pass was worthwhile. If you're based in Osaka or Kyoto and go to Hiroshima, it's pretty much worth it just for tag trip.

You can see Fuji out the window for a decent amount of time, 10 minutes or so?

Shinkansens always put me to sleep.

Oh, the reservation thing - definitely worth doing. You can do it half an hour in advance if you want to though, which is mostly what we dd.