I think Dybala would perform better as a 9 or a False 9 than he currently does, but even that isn't his ideal position imo. He'd perform better, and it would suit his particular talents better, but I think it would make us very one-dimensional.
He's looked best as a secondary/support striker, playing in a front 2, especially when looked at in the context of playing with the team instead of on his own. He works best when playing beside a target man type CF, who can hold the ball up, and lay it off to him around the box so he can work his magic, or little one twos with a CF like Mandzu (Dzeko would be another that suits this game). That and a mezzala like Pogba (or a creative CAM, think De Bruyne or another of that sort) playing in the mid behind to dictate play and create chances. 3-5-2 and 4-3-1-2 would suit him best imo, as it would take the creative burden and dictating of attacks off his shoulders. He just doesn't seem to have the vision for it, and isn't really developing it over the past couple years. And Ronaldo really isn't going to suit either of those formations playing as that target man beside Dybala. I'm sure he could do it, and it would be passable, but I doubt it would get the best out of Ronaldo.
People compare Dybala to Aguero, and say he should be played as a False 9, spearheading the attack. But even City most often played with Aguero paired with a CF like Dzeko in the past. Even now, with Pep, king of midget forwards, he's often played beside Gabriel Jesus.