"no thanks" is used when u politely want to refuse something
"you're welcome" is used when someone thanks u for something or when they are grateful to u for something
So no, they cannot be interchanged, they have different meanings.
No, they mean different things. "No thanks" is a polite way of saying "no" when someone offers you something, while "you're welcome" is a response to "thank you."
"Do you want some food?"
"No thanks, I don't want any."