I'm wondering what flow through the nose is like if you have adequate space in your nasal cavity. And vice versa, if less flow through one nostril means you have a small interior nose space? Is it normal for air to 'choose' mainly one nostril to go through?

For me there is always one nostril with great flow and one with barely any flow. I mainly feel a difference in temperature when I hold a finger under that nostril, because the tiny bit of air that leaves is warmer than the air that goes in. Sometimes it feels like no air comes through and it feels stuffy. 

When I close the nostril with a lot of flow, the nostril with barely any airflow will now have a lot of airflow, often without resistance or a little bit resistance, sometimes with a lot of resistance.

When I'm lying on my side, it's usually the side on the bottom that's barely having any air flow.  I feel like the amount of snot is totally normal though and not the cause. I think that the interior of my nose is small and that's why even a little bit can decrease airflow.

PS: This might be one reason why I like to sleep on my side and turn a lot: every time I turn it increases the airflow in the nostril that's barely having any flow...before the other nostril will have decreased flow....
I think on my back it's the worst (stuffiest), except when elevated, then it's actually better. But I would have to pay attention more to confirm.