I ride with a spine protector (and a helmet) inbounds, every day. I've never injured my back had been riding for years before I decided to get one.
I figured it was a good idea since the reality is we're riding pretty damn fast and/or doing tricks on, over or around trees, cliffs, rocks, jumps, ice, other humans, and rails/boxes if you're into that.
It's super comfortable and does not impeed my riding in any way, I find a backpack is more of a hindrance.
Mine is a Demon and I'm very happy with it, but that was all that was in the shop so I've never even tried on another brand.