I have just watched a few of the YouTube highlight compilations. Obviously, anyone looks great when you watch their highlights, and my conclusions are hardly a surprise, but here it is: the power will play to all fields.
He has amazing plate coverage. People try to pitch him outside to take away his power, and it simply doesn't work: he was routinely hitting outside pitches ten rows up the bleachers to right in Detroit. He hit a ball *over* the pool in Arizona. He basically flicked a few HR balls inside the RF foul pole, which I expect to be an even bigger part of his game in Boston. He put one high up the batters eye in Colorado. That ball is in the camera well in Fenway.
A ton of his HR to right have a fairly low, line drive-like trajectory. He will skip a ton of balls off the RF wall or into the bullpens at Fenway. But he hits more moonshots to left, some of which will bounce off the parking structure.
Also, he has multiple HR off some pretty good pitchers: Kluber, Cody Allen, Carrasco, Sale, Quintana, Bumgarner, Kershaw, Tanaka.