Part of me just wants to start on normal so it goes faster, but I doubt I'll do that. Might as well kill two birds with one stone and level as fast as possible.
I think it makes sense to just do normal and go as fast as you can to be honest. Because the faster you get to adventure mode without being 70 the longer you can just grind out rift fragments without actually doing rifts (as it's kind of a waste if you aren't 70). 2.1 isn't out so rifts will still be 5 fragments (unless they purposefully changed this on consoles ahead of time) and it's unlikely RiF will be a thing on consoles given how long it would take to invite someone because of how the console games are set up.