I think I understand why you see Kawhi similarities (or some other big wing like Giannis etc), but I don't see it fully translating because of balance. The moves at the timestamp here and the 9:35 one are ambitious and that's fine, but when I think of young Kawhi (and now Williams) I remember him being very balanced on his shot attempts. Even moving through the air, just straight up ad down bodywise and solid, repeatable form.
I don't necessarily see Achiuwa presently having that consistency of form. It's more erratic, even if he makes the shot. It's missing that moment when people realized, damn, Kawhi's mid-range game is money. Because each shot looks so sturdy. And Kawhi of course kept adding moves to his repertoire, adding the Kobe into his post-ups, adding the spins like Tony, etc etc. But it started with a great base of a shot that was sound body-wise and that he could repeat.
I might make a Williams video or a long series of posts linking to videos with timestamps to show why I see more scoring wing potential for Williams.