this is the best case for a perfermance review because it's

"不與salary raise掛勾". I think you are on a very good path and working environment with your supervisor and your boss. Seems they care about you and your career. Listen to what they say and think. it is very reasonable to find out your big boss's expectations on your career development. Just talk to him and ask him directly such as "I'd like to find out your expectation on my career development..." etc...