Relaxed isn't the way to go, because that 60 speed tier is pretty full. It can outspeed a good number of walls and bulky attackers. 65 is pretty good when you consider what its role is.
Eiter way, both of its attacking moves are utility and nothing more, we shouldn't sacrifice speed for a miniscule amount of damage more. I checked, the boost to special attack with bold is 10, and the boost to attack with Impish is 13. BUT, considering scald is its main move, and many sets won't be running knock off, I now strongly feel that bold is the way to go.