If the Poke-Power says "As long as this Pokemon is on your bench/active" then you can only use the Poke-Power when it's benched/active. If it doesn't, then you can use the Power as long as the Pokemon is in play. I think Poke-Bodies are always used unless they are turned off due to Cessation Crystal/Lati-Lock/etc.
For your example, you can use Extra Boost if it's benched or active, it doesn't matter because it does specify that it has to be benched/active.
I think this is all right, and I hope I've helped.