I'm not surprised you have questions like this after being certified for Nitrox via Padi. Fundamentals will actually teach you more about best mix and standard mix. Do some self study and brush up on the math before doing the course using the Daltons diamond equation etc. All diving is somewhat technical and in my opinion all divers should acquire at least that level of knowledge which Padi most often fails to teach.
As long as we're hijacking this thread, let's go a step further and keep in mind that no one has ever been "nitrox certified by PADI" nor does PADI teach (or fail to teach) anything. INSTRUCTORS "teach" and INSTRUCTORS "certify." I learned about best mix, standard mixes, Dalton's diamond, etc from a PADI instructor. Hell, that stuff is even in the course materials.