Opening 1NT with a 5-card Major

Playing a weak no-trump, you can choose whether to open the 5-card major or 1NT because if you open the major you can make a minimum rebid (or pass a simple raise or 1NT response). Like you I quite often open a 5-card major if i have one rather than 1NT - you will often miss a 5-3 fit in the major if you open 1NT. Playing a strong no-trump, you will often have an impossible rebid if you are in range for 1NT but open the major because you do not want to make a minimum rebid (or pass partner’s 1NT response, which could be up to 10 points for strong no-trump players) with 15-16 points. After 3C is doubled, pass should show no preference, so West’s 3H is fine. Regarding the shape, I agree you do not want to overcall with a 5332 shape. sometimes you have a 5-card suit and a 4-card suit or even two 5-card suits, in which case you do not want to have always to pass. You cannot make a takeout double of 1NT because double would be for penalties. Sometimes if you are short in one major and have four cards in the major, you could pass first time with the intention of doubling if responder transfers into your short suit.