If you want to say something, e.g. ideas, meanings, relationships,etc., I think 微妙 is actually the perfect word. One thing though, as far as I know, 微妙 is not used to describe people. We cannot say 他很微妙。
Maybe you could say it in a more sarcastic manner, like "You think you're so cool?"
Then, you could use:
"你是不是觉得自己特狡猾?" - Which kind of means "You think you're so sly/cunning?"
"别觉得自己有多聪明/狡猾/酷." - Which means more along the lines of "Don't think you're fooling anyone with your 'cool-guy/smart-guy' act."
Both of my translations are really colloquial and informal though, I'm sure others will come up with better ones