The short answer? Be yourself.
If it comes naturally to you, go ahead and bring spirituality into your classes. As long as your facility allows chanting and that you teach beyond asana-only, students love it and tend to think of you as more ‘authentic’ and they’ll often even think you have more experience than you actually do.
However, if you feel uncomfortable leading a chant and you question some of the deeper benefits of certain poses, don’t go there. You’ll risk seeming like a fraud and your class might feel quite awkward.
One way to decide is to put yourself in your students place. If you teach beginners, remember how you felt as a beginner. When I was in class as a beginner, I was SO uncomfortable when the rest of the class was chanting and they all seemed to know the words. I felt like I was the only clueless one and I wished I could hide. When I started teaching, I never forgot that feeling.
What works for me is an asana-based practice with a mix of English and Sanskrit and lot of breathing work and mindfulness elements. I don’t get very spiritual and I don’t chant at all unless I teach pre- or post-natal yoga when I simply offer three om’s at the end of practice (the volume and calming sound seems to really benefit the babies). I do believe certain poses offer benefits well beyond their obvious physical rewards and I think western medicine is even catching up in that department. Because I teach this way, I don’t adjust my style based on location.
Now, what works for me and what works for you might be totally different and that’s the beauty of modern yoga – there are so many options available so we really can say there is a yoga for everyone!