On the Pro of the Check In, as someone who trained a lot of people on Universal Hotels you can do an "Early Arrival" as early as 8am, the rooms aren't guaranteed until 4p, but I've gotten my room as early as 9am before, latest I ever got my room was 5pm at Hard Rock during Covid. Aventura is normally pretty good about the early accommodations. Like 10, 10:30am.
Be mindful of the resort amenities, you definitely can & will get away with using their pool, and the water taxi, but "On Paper" cross amenities is technically supposed to be for your hotel category and lower. I can tell you, that honestly, no one cares, and the guest who pool hop & use the water taxi actually bring additional revenue to Sapphire.
Skyline View starts at the 9th Floor. Kind of a bummer honestly. I've had some amazing Skyline's and some kind of mid ones. My favorite was actually a Deluxe Skyline King on the 12th floor. Perfect view of the Hogwart's Castle in the morning. Also had an awesome view on the 15th floor sweeping over I4 and Citywalk.