i personaly hate bubble counters since theyre only realy usefull on pressurised co2 setups. 14 bubbles seems ok, it will get faster though before getting slower as the yeast dies because the contents of the bottle have become too acidic, mine gives about a bubble a second, its more or less a constant stream from my airstone, and yes everytime it goes through the power head youll get a spray of bubbles, according to tom barr plants prefer a mist of bubbles across their leaves to stimulate good growth but in my tank i seem to have good growth and pearling with just an airstone to diffuse it (co2) into the water. so i dont suppose it realy matters if you dislike the powerhead method dont be scared to experiment until you find a method you like, and try not to worry about being 100% right with everything since theres more than one way to do things yet they all the the same result, better plant growth.