Soto's power is the only thing that isn't plus-plus elite. He sprays the ball like Trea Turner, he draws walks like Joey Gallo, and he has the batting IQ of Manny Ramirez. He's doesn't need to improve anything, but he's still young enough to learn to loft the ball.
Re: Soto vs. Guerrero, the safe bet is definitely Soto. Any player that dominates the league starting as a teenager is historic until proven otherwise. For comparison, Vlad was a year away in the minors at an age when Soto was carving up big league pitchers.
However Guerrero's ceiling is still higher. His raw power and bat to ball ability is just something you're born with, and Soto is just a step below.