Should be Limitless + Six Eyes
Limitless by itself isn't nearly as strong since you can't finely control it
6 eyes + Limitless combo is > Shrine imo
You're right concerning the first part.
Though we still don't know what Shrine is actually. Sukuna isn't the King of curses for nothing I guess.
Even Gojo himself admitted he couldn't destroy even one of his fingers.
1- Gojo stated Yuta could surpass him (implying he didn't yet, I know, but still...)
2- We've seen that many Heian era sorcerers were ~Yuta level.
3- Yuta did struggled against 100% Ryu (high diff), and he needed Uro's CT to trick him.
4- 15 fingers Sukuna neg diffed Ryu with one casual move (making Uro shitting her pants just by "being nearby").
Accordingly: 15 fingers full serious Sukuna should be >>> current Yuta.
And he still hasn't revealed his full potential yet, even with 15 fingers, so imagine 20 fingers Sukuna.
Dude is both a CE/CT monster and genius.