-
Generally, any suite you find labeled Standard Suite is in the SUA upgrade pool, yes. And a “premium” suite is not.
You are also correct that you CAN be further upgraded to a Premium Suite at check-in at the discretion of the hotel.
I’ve definitely had luck being in a Standard Suite where the Premium version had a balcony and asking politely for a balcony suite and getting it easily.
All is property dependent.
And sometimes there are two or three standard suites that are vastly different so always look at the website rooms page and call while it’s up if they aren’t marked.