Hello, Juju. My existence proves you wrong.
Ambreg, I don't do much with runes or sigils, really, so I can't answer that specifically although if I were to do so I would most likely agree with Raven. On the topic of magick, that is basically the manipulation of energy and I mix energies all the time. So long as you don't overwork yourself, which is a risk in any type of practice no matter how basic, you should be fine. I also mix beliefs, being a Christian-Taoist-Buddhist who also practices Japanese Shinto.