You don't need a computer unless you want to track data. And you can calculate candence in your head while riding: No. of pedal strokes/15 seconds x 4=strokes/minute.

Bottle vs. Camelback is like trailer vs. panniers. Both have advantages and disadvantages. In the end, it usually comes down to personal preference. I tour with a Camelback and bottles. Only once did I use a Camelback for a road ride and that was because it was a hilly 76 mile ride where the starting temp was in the mid 80s and the forecast high upper 90s with massive humidity, and there was very little shade on the ride. In the end, use whatever allows you to carry enough water for conditions.