Do repuations give discounts for being higher rep? Ex. Would i get cheaper mounts and training for gaining rep with my races faction?
Unless my memory is off, yes you do get discounts on repairs, vendor items and mounts if your rep with that faction is honored (I believe), 10% maybe? Sorry been awhile 
Yes, Yep, Yeah, and YaYa
10% for honor and 10% for… pvp rank6 and higher? I forget the pvp min requirement it is up there though.
But the only rep I even paid attention to was Furbolg, so none of the benefits are critical.
Honored gives you a 10% discount on everything from vendors associated with that faction. Unfriendly or below, vendors associated with that faction won’t talk to you.
Nothing else makes a difference.
If you want to buy a different races mount you need exhaulted