If you're talking about duels those opponents have apparently always been fake and randomly generated with their level based on yours and their deck power based on league. If you're talking about the tournaments then I don't know, it kinda seems like it could be real people, but it's also weird that there are so many people consistently wasting points not going for the win and only getting bronze.

As for the game, It's not really that great, but at the same time it's so incredibly stingy that it barely takes any time at all to play, you can spend only minutes a day checking up on it and be playing at almost maximum efficiency. The prices though are definitely a joke and no one should ever spend anything on it.