yep! both Timmy Turner and Poof are voiced by Tara Strong. She was also the voice behind Twilight Sparkle, Bubbles( from The Powerpuff Girls) Ben Ten( in the original series) Raven( Teen Titans & Teen Titans Go!) Dill Pickles( Rugrats and All Grown Up!) Terrince( Fosters Home For Imaginary Friends) and much more.
actully,you are wrong, poof is a boy and is played bya girl(so poof was played by a girl or sound effects did poofs voice),thats why poof never talks that much and only say poof poof)2:timmy was played by a girl for only one season,but then the voice(girl playing timmy)died.so they got a new person that sounded like timmy.(weaird fact:danny fantom is timmy)