It seems that 되다, 좋다, and 괜찮다 can all be used to ask for permission, or whether something is advisable:
담배 피워도 좋습니까? May I smoke?
한국말로 물어도 돼요? May I ask in Korean?
음식이 매워도 괜찮아요? Is it okay if the food is spicy?
Is there any difference between the use of 되다, 촣다, and 괜찮다, or are they basically interchangeable in meaning and tone?
Also, I know about the use of 면 안되다 to deny permission, but they all be used to deny permission or say that something is inadvisable? Can you say "담배 피워도 좋지 않습니다" or "음식이 매워면 괜찮지 않아요"?