To add? I've just seen this on one of your other posts:
Arrive in Rome @ 8 am ( stay 2 nights in Rome)
Unless you've change your itinerary to add more time to Rome, this pretty much leaves you just one full day for the Eternal City, and that is the one you'll need to dedicate to the Vatican. You do NOT want to take on the vast, HOT and crowded museums all jet-lagged from an international flight (if indeed you will be coming from a different continent). As well, airline schedules have not been exactly trustworthy lately, and many airports have been sort of a mess. You don't want to book anything for arrival day that you might not be able to make due to flight cancellation, late arrival, delayed baggage issues, long immigration lines, etc.
Since you plan to be arriving late August, I'll assume that you know that the museums are closed on Sundays except for free entry/shortened hours on the last Sundays of a month: definitely not a day I'd try to go even though some tours are available through the Vatican's site for that day.
https://m.museivaticani.va/content/museivaticani-mobile/en/organizza-visita/consigli-utili.html