Originally Posted by: SvanholmCan I mix between, lets say, E minor pentatonic, E minor(aeolian) and E blues scale while jaming to a backing track in the key of E?

As Slipin Lizard observes, you can play anything you want, any time. In the end, the only issue is: do you like the sound of the notes you are playing?

Having said that, there are notes, scales, licks that you will probably like more than others. So, a lot of practice, trial & error is necessary in order to build a vocabulary of things you like. Of your own style.

So, use all those scales! Use other ones, too! And learn to target chord tones so you can think it terms of what the chords & bass notes are in the backing track. That's very important to do so your playing sounds integrated, like it's working with instead of against the backing track.

It's more important to think in terms of: what sound do I want to create here?

Try a lick or scale. Does it sound good over a certain chord? If yes, remember it. Work on it, refine it. If no, then avoid it in the future!

After you get familiar with lots of scales & licks, with how to play over chord changes, to use different positions of scales to target chord tones, then you will get to the point where you'll know which scale to use based on what sound or lick you are trying to create at the time.