My two cents: read Cidermaker's Handbook. It's got great information on apple varieties, sugar levels, TA, PH, analysis, etc.
I get juice from a local farmer's market, unpasteurized. We ferment it dry, and sometimes add sugar and bottle to get sparkling. It's usually pretty bland so we add tannin and oak chips while it's aging, which helps a tad.
We did a test with several wine yeasts and White Labs English Cider. White Labs seemed to retain the most apple character, whereas the others ended up pretty much bland dry.
This upcoming year I'm hoping to get true cider varietals from an orchard in VA. That should make a big difference.
Our 2015 batch had sulfide issues. We used reduless, which seemed to work. However, I just opened one of our last bottles and it has an off odor and taste. My wife says it smells like pennies. I think it has a strange hint of cocktail sauce(?). My only guess is that it's either gone bad, or the reduless/copper has done something odd 5 years later.