Based on HS tape, I give the edge to Brinson and George. Not sure anyone else though.
Rambo was more than 4th/5th string at OU lol. He got passed up. But I wouldn't call his bio from UM's official website thin by any means: "Finished career with Sooners with 76 catches, 1,180 receiving yards and nine receiving touchdowns…Played in 2019 and 2020 College Football Playoff…Had best season of career in 2019, finishing with 43 catches, 743 yards and five touchdown receptions". If he had stayed, he would still have seen a lot of snaps.
IIRC, the reason he got passed up wasn't talent, but he was inconsistent in his routes and with his hands. Same problem lots of our guys have experienced. Even at Miami, he struggled in the Spring and didn't really get unleashed until TVD went on his tear.
Net/net, kid is going to be very hard to replace. Probably more committee in the first few games of the season at least, until someone emerges. But we have talented WRs, a potentially transformational QB and a top notch play caller. They'll be in a position to showcase their talents.