Hotel: Bellagio
Room Name/Type: Premier Stay Well King

Check-in Day: Saturday 10/8

Check-in Time: 2:00pm

Upgrade: nope

Late Checkout: yes, 4pm

Breakfast Credit: same as above

Misc Credits: same as above

Some Comments
1) Check-In: messaged hotel via Amex to confirm 2:00pm check-in, checked-in via app, was notified at 1pm that my room was ready and my digital key was available. When I arrived, check-in line was easily 40 minutes long. Went to elevator with my digital key and accessed my room. Easy. Would I have gotten an upgrade if I waited in line, who knows? But I got 40 minutes of my time.
2) Food and Beverage Credit: went to lunch at Spago after dropping my stuff in my room. Bill was approx $53 plus tip. After returning later, checked via app, only charged for Spago tip. On check-out day, went to Eataly @ Park MGM (highly recommend), sat at Gran Milano bar and ordered wine/food. It was 3:57. Asked them to close out my bill. Checked out via app 1 minute later, only charged for Gran Milano tip.
3) Breakfast Credit: First day: used $43 at Sadelle's, $7.00 for latte at Cafe Gelato Second Day: Used $63 at Sadelle's, $7.00 at Bellagio Patesserie for latte

My take away is that Breakfast credits and Food and Beverage are automatic. Not driven by time of day, just by where you used it.

Made reservations at Sadelle's approx 10 days before. Line for non-reservations was INSANE.