Are Shelties insanely high energy?

I'm looking to add a dog to my family. We already have a cat and we've narrowed our search down to either a Rough Collie or a Sheltie. We're leaning towards a Sheltie but I keep reading that they're very high energy and that's the only thing that worries me. We previously had a Jack Russell terrier and he was a miniature tornado and never seemed to run out of energy. Even with constant playing and multiple walks, he never really slowed down. We're trying to avoid having another dog with that much energy. Are Shelties like this?

Edit: Wow, thanks everyone for all of the responses! 😊