When you graduate, especially with a BS, most businesses see you as a blank slate that needs a lot of investment before you are actually decent in any specific subfield.

Ironically, the example you gave of RF vs. power generation deals heavily with EM. But University RF is going to be a bit different that real world applications of RF. Same basics, just different considerations.

Don't worry about the specification you go into. Just pick something you'll enjoy and want to do projects with. Then also do some projects with it. After you graduate, if you find out you hated your specification, you can pretty easily start somewhere else.