Panama City Beach is one of a handful of resorts that does "upper level" and "lower level". It also has 1BR and 2BR Deluxe and "standard" units, which further complicates things.
So if you booked a 1BR lower level and a 2BR or 2BR Deluxe lower level and 2BR Deluxe Upper level was available, you would upgrade into a 2BR Standard lower level.
If in addition to that a 1BR or 1BR Deluxe upper level was also available, it would give you a choice to upgrade to "better view" to a 1BR Deluxe Upper level, or "bigger room" in which case you would likely get the 2BR LL.
It's rare but I have seen instances that the "bigger room" option presents more than one room type option, and you have the ability to choose between suites. At Ocean Blvd I was once given the choice to choose between a 2BR Deluxe Upper Level Ocean View in tower 2 or a 3 Bedroom Deluxe in tower 3.
Upgrades seem to sometimes be more complicated than they should be. Flexibility in your travelling schedule and your willingness to travel out of season will give you the ability to get upgrades more often than not. At least that's been my experience.
The resorts with a ton of different room types, like Ocean Blvd are some of the most difficult to predict, but you can also get absolute value gems. I upgraded in January from a 1BR Deluxe Lower Level in tower 2 which is the cheapest room type in the whole facility, to a 2BR Deluxe Ocean FRONT Upper Level in tower 2, which is one of the more costly units. Combining that with the 50% off sale Wyndham was running in December, I got 8 nights in that unit for 22,000 points, which is insane.