Just came back this morning.
Few tips.
Earliest check in time is 12:30pm (for ART swab + wait for results etc), and boarding only opens at 2pm to physically board the ship.
App allows only one bumper car reservation session but you can just turn up, they don't check and usually let you through. It is not very crowded.
FlowRider opens on the first day, just queue once you get on board, wasn't much people at 2pm. Reservations (free activity) for FlowRider opens at 8pm on the first day, for Day 2 and Day 3, limited to 20 pax per half hour slot with one reservation max per pax. This sells out quickly too.
Bionic Bar opens at 6-9pm on Day 2 and 3.
They will strictly break up your party into 2s for dining if you eat/drink "out", though long tables can have 2 pax on each end at Windjammer and main dining area.
No more my fixed dinner timing/tables at the main dining, just turn up and queue.
North Star reservation done on app and was sold out quite quickly. US$20 per pax for adults and US$10 per pax for kids.
Rock climbing was pretty popular too, with queues.