I wanted to know if being able to count the notes and understand the notes are all there is to know to rhythm.
No. Not even close.Six quavers in 6/8 time has a different rhythm to six quavers in 3/4 time for example.You need to understand note groupings, the feel of particular types of piece (a waltz, minuet and Mazurka are all 3/4 time, but have a completely different feel to them), where the accents fall and a whole lot of other stuff. Just counting out note values won't get you there.Why are you doing the Rach Sonata now? It is not the best use of your time. Lay some solid foundations so that when you are ready to play it you can do it justice.
It's relieving to know that there's more to it than the note values and time sigs. I would really love to learn more but I'm not quite sure how. Like I said before, most books that I've looked at stress the basics -- note counting, time sigs, general rules for where accents lie in the beats of different musical genres, compound/simple time. No book that I've looked at really develops that. Do you have recommendations?
There's really no other reason for why I'm trying to play Rach's Sonata other than because it sounds good. Why does knowing note grouping for pieces that aren't written by Rach useful for "doing this piece [Rach sonata] justice"?