As for genre classification, well, space opera is 100% a sub-genre of science fiction. It always has been. In some ways it is the oldest and definitely the most prolific. It was born from the Planetary Romance genre which gradually expanded from settings on a planet to different planets and then different planets in far flung system. The nature of the stories remained largely unchanged. The supernatural is a frequent trope as is swashbuckling adventure. Asimov tended to do more cerebral puzzles in his space opera, but his technology was no less improbable or fantastic.