When we talk about favourite genre I think I have kind of mixed taste and it really depends on my mood what I want to watch but generally I think my favourite genre would be Psychological and mystery. That is what gets me going the most....

Becoming a demon would make him lose his mind that will be threatening to everyone around him. But As we know Tanjiro is very good at maintaining concentration at hard times, that might help him from not harming his friends. But his power would go insane.