"You cannot preempt in fourth seat. To understand why, think about why you preempt --- to make life difficult for the opponents. Clearly, if the bidding starts with three passes and you have a bad hand, you should simply pass and move on to the next deal."   Seagram & Smith

It is nearly always bad to have high cards in a suit where partner has a singleton or void. These are called "wasted values".

"On those sequences where your opponents have shown a fit and limited values, your attitude toward reopening should range from strongly inclined to obsessive.  It is almost inexcusable to allow your opponents to play at the 2 level when they WANT to do so."   Mike Lawrence

1NT with a weak doubleton is okay. However, don't open 1NT with a 5-card major and Two unstopped suits. Also don't open INT with an excellent 5-card major AND a maximum 17 HCP hand.