The cables look fine, though I'll defer to another's "expertise" on why they may need to be specifically one way or another. WRT the rear brake cable, that's how I've got mine routed, as you've taped yours, just below the seat post, and *not* adjacent.
The shifters look high to me; I'd have them a bit lower, but as you say, that's a matter of personal preference and comfort.
Nice looking bike!