Flats work great for the pop rock genre (Maroon 5's first album kind of music). They're mellow and they sit in the mix very well, especially on a Fender

If you want to record with flats I would recommend breaking in the set for a least a month prior to recording to get the traditional thumpy flatwound sound. Flats sound rather bright out of the box until they're broken in.
If the strings have silks on the end of them, you can identify what kind of string they are. For example, Fender strings usually have black silks, and Rotosounds have red. If they don't have any silks they can be a number of brands. D'Addario uses blue silks on their Chrome flat wound strings, and they have colored ball ends on their XL (green, red, chrome, black).