Since 1975 16 USC QBs have been drafted into the NFL.Carson Palmer, Matt Leinart, Mark Sanchez, and Sam Darnold were 1st round picks. I do not believe a USC QB has ever been extraordinarily successful in the NFL.
I have seen Caleb Williams play about 10 times between last year and this year. I thought he looked better last year. This year I thought he was very inconsistent, and at times underwhelming. I admit I am not an expert or NFL level scout but I thought Caleb Williams showed some troublesome issues this year. His decision making at times looked very suspect, especially under pressure. His accuracy looked bad at times too. Of course NFL coaches can really help young players develop in a short amount of time. But before I draft Caleb Williams at #1, I would want to talk to him and hear how he talks about football. I would want to measure his football intelligence.
The history of USC QBs in the NFL has been been good. I would be very careful drafting Williams.
I thought Penix was the guy who could transition to the NFL faster than any of the others. You can see his accuracy, especially throwing the deep ball. What a weapon, if you have the receivers. Then I saw him play against Michigan and under pressure he looked like he was not the same QB. I still think in the right system with a decent OL, he could be an immediate success, but always keep in mind most college QB do not achieve success in the NFL.