You can mix anything you want. It has to be your ear that decides if it sounds good or not. For example, think about a blues progression in E using all seventh chords. Some guitarists will just play E minor pentatonic over it. Some would use major pentatonic or a mixture of both.
Others might use Mixolydian over each chord, i.e., E Mixolydian over the E7, A Mixolydian over the A7 and B Mixolydian over the B7. You could combine all of those scales if you wanted. For my personal tastes it would sound like someone trying too hard if they did that. Others might like it. It would also depend on how good you are at transitioning between each change.
There are no rules but if you do something for the sake of thinking it will add interest then the chances are it won’t. At the end of they day there are twelve notes in Western music. If something calls for a Major scale then try to get creative with those seven notes with perhaps a sprinkling of “wrong” to add tension and interest. If you play too many of the five remaining “wrong” notes then it’s likely to just sound bad.
It’s just about finding what you think suits the song. Some songs work well with a mix up, some don’t. This has to be your ear that decides. I was playing over a backing track recently. Technically, I could have used any number of ideas but in the end the only thing that sounded right was a plain old minor pentatonic scale with very few outside notes.
