Of course speed and configuration make a difference.
However, for a given configuration the attitudes required should be pretty much the same each time if you are flying the correct speed. If it isn't working, you adjust the attitude as required to fly your 3º slope.
Floating up and down on power without a fixed attitude is more akin to needle chasing - OK it gets the job done but it is not the best way to do it. "Good enough" is not necessarily good enough!