Except if you don't aim with flashes and stuns you won't be able to get the proper effect. A stun or flash that lands further away has less of an effect on the enemy player. An EMP grenade that lands 500000 feet away from the player EMPs them, period. Even if the player is on the second floor of a building and you throw an EMP that lands outside the house.
No, the range is completely different given distance to enemy player + effect on player.
As I mentioned earlier, stuns and flashes that land far away = less effect on player. If you're going to allow EMPs to hit through 2 buses, or a whole house, then it should effect you based on range/distance to enemy/affected player.