I'm not seeing the McGrady comp for Wiggins. Similar bodies at the same age but ballhandling and passing were huge parts of McGrady's game. He had the skills and was afforded the responsibilities of a point forward. Wiggins is solid in those areas and has years of development ahead of course but he's way behind at the same age and just doesn't seem like a point forward type.
I think Wiggins is more along the lines of Paul George. Similar body types and athleticism. He could be a two-way player who creates for his teammates, not with extraordinary playmaking skills but from a willingness to hit bigs on pick and pops and drive and kick to shooters. I think Wiggins is a bit more explosive on his drives but he may never be the long-range shooter George is.
Parker has broad similarities to Pierce: He's a wide small forward with all-around scoring skills. Stylistically though, he's closer to Carmelo. Unless improved conditioning improves his quickness, it's hard to see him being equal or better than Carmelo at anything besides going coast to coast off the dribble. His first step is worse. He struggles to finish around the rim against athletic defenders just like Carmelo but doesn't make up for it by being excellent at grabbing his own misses. He has similar black hole tendencies but hasn't shown great intermittent passing chops.