I'm a principal at a non-fang company. Throughout my tenure however, I've worked at roughly half of the FAANG companies back when people thought of them as synonymous with excellence. The jury is still out as to what that really means today, but I digress.

In any event, the only single takeaway that I've come to regarding Staff is that the role is executed vastly differently across organizations. I think that the most anyone can tell you is "how it worked in my experience".

With that caveat, my experience has been that most of the time Staff is a bastardized hybrid between management and SME work with a respective ratio of 80/20 or 60/40 in my experience at G. Some orgs are highly stratified with strict handcuffs to the keyboard, strict roles, strict ownership assignments. Some are less stratified, with more dynamic on/off seasons of management, floating ownership, consulting roles, or any mix of the previous. These less stratified orgs tend to treat Staff as "trusted seniors" with nothing substantially changing after the jump.

One common thread is the emphasis on crossfunctionality. You now get to work outside your senior cage with other teams and have the privilege of getting thrown onto PoC projects or chosen to bear the burden of the innovation lab experiments. I say that half joking, but it is nonetheless a fun privilege. The other common thread is "trust". In a phrase, "We trust you more than the senior who has idled in that role for 5y at 3 different orgs. Your title means something a bit more." Helps with conferences and calls. The other thing that I've noticed is that you're now the new "senior eng" to be picked by the Principal or DE for their pet project. That can be a plus, but the point here is that Senior and Intermediate/Associate is just not considered. The last thing that I'd say is that promoting to Staff within an org means a whole lot more than incoming as a Staff. The trust factor is increased, you're a bit more bonafide. I suppose that goes for most roles though.