Stealth is a new keyword ability that lets some characters strike from the shadows without fear
of reprisal. When choosing which enemy to attack, you must attack a character without stealth
if able.
If my opponent has one tapped character with stealth, and the rest of their creatures are
untapped, which character can I attack?
[Source: WotC] 
Stealth doesn’t override the rules for attacking tapped/untapped characters. Since the
tapped character is the only one that can be attacked, that’s where your attack is headed.
Brave and stealth essentially cancel each other out. You must attack that character if able,
and you must attack other characters if able. This basically means you must attack a character
you can attack, the same as if those abilities weren’t there.
Razorclaw’s robot mode ability says that when he flips to that mode he can attack untapped characters that turn as though they were tapped. If a character has Stealth when untapped, does Razorclaw treat them as tapped or untapped for the purpose of their Stealth?
[Source: WotC]
The character will still have Stealth.
Razorclaw’s ability changes the way that Razorclaw can attack but doesn’t actually change the Tapped/Untapped state of other cards.
The opponent can choose to attack any available target; they essentially cancel each other out.
