1. An app that runs without root won't run "better" if the phone is rooted. If the phone asks for root access on an unrooted phone and doesn't get it, it doesn't run. If it doesn't ask for root access, it'll never know that the phone is rooted.
2. Try
Sprint Samsung Galaxy Note5 - most of the people who discover root exploits post them there first.
Hmmm, no disrespect intended but I'd have to disagree with this, "An app that runs without root won't run "better" if the phone is rooted."
There are apps, I guess I"ll use Greenify, that if it has root access, it will actually close apps, without having to ask to do it. It's been awhile since I was rooted, but I remember that greenify had the best results, if rooted. File managers are the same, in that with root, you can access some root files, that you normally wouldn't be able to with the same app, unrooted.
Perhaps I misunderstood you, and I apologize if I did...but "some" apps are designed to run more efficiently (better) if root access is achieved.
Thanks Sir, for allowing me to, probably misunderstand what you meant...lol!