Saka more consistent and finds a way to get the better of his fullback reliably via intelligence, ball control, a quick few yards and smarts. Reminds me of Ribery in that way.
Foden probably has more potential. Not sure what his best position will be. I'd guess the one Isco played when he replaced Bale at Madrid, where you have a wing forward on the left, a 9, Foden tucked in on the right playing as a 10 or RW whenever he feels like it, then a really attacking right back who overlaps and a midfield 3 with one guy who can attack and get forward like Modric did. Basically he's a much worse Messi but far more similar to him than most players are stylistically, which is good enough to be a top 2 or 3 right-sided attacker in the world at his peak.
The other path is as a 10 and in some ways, leaving City to go play as a 10 somewhere would be good for him if the goal for England is for him to become their Griezmann, with Bellingham as Pogba, a tackling DM/CM type with Rice as a bigger but slower Kante. But unlikely obviously. More likely is that Pep leaves for whatever reason and the new manager gives him De Bruyne's job in 2-3 years when De Bruyne is a sub or moves on.