Did they change their style?

I don't think they even change their styles, probably modifying it though, but not really changing because they do have a signature tune which you can't really compare to other artists.

I am not too big a fan, but I think they just revamped their style if anything. With more notoriety, they have been able to do more songs as the feature artists, and more songs featuring others. I think Adam Levine has a very soothing voice, so it's always interesting to hear him alongside another singer.