Don’t worry! The genie does not “third wheel” your holiday. Most of the time you will see your genie 1-3 times per day. At a minimum they stop by when you’re having dinner at the start of the meal to check in. You will also see them if they help you disembark from the ship (they use their priority key for the elevator for you), or go to an activity they have organized (flow rider session, bridge or galley tour, etc ) or when they have selected seats for you at a show. Otherwise you just what’s ap them a lot to ask for things (room service, schedule changes). They are deliberately non intrusive.
when we first did Star class we also thought that we would not use the genie much… I found we used them more than we thought as its very convenient to have someone who can customize your every whim.
we still cruise the majority of the time in sky class, as the pricing is somewhat more reasonable (not trying to say current pricing in either category is where I want it to be) and we overeat less in sky class.
if you are torn, I would choose sky class, and see after you do it what your impression is. If you aren’t sure you would love the Genie, don’t pay double for Star class.
in answer to your other questions, in sky class you still get your arrival window, but can come an hour earlier. In star you can tell them when you want to get there from around 10:30 onwards.
sky gets beer and wine after 11am in the suite lounge, cocktails etc during the evening cocktail hours.
for disembarkation at the end of the cruise you can go to the suite lounge and the concierges will escort groups down. The genie goes a little further and walks you to your luggage bypassing more lines etc.