You're correct that Part 3 is a lot more episodic. This is because Araki wanted to spend a lot of time experimenting with stands and fleshing out the new power system. As the series goes on, the stand battles become more strategic and the powers become more unique. Some people think Part 3 is one of the weakest parts because the stand concept wasn't fully realized, and the anime adaptation is a bit slower paced. That said, Part 3 is even more bizarre than parts 1 and 2, so it's a lot of fun if you think of Stardust Crusaders as a long journey with your crazy friends!