A few simple ideas which may help.
To overcall 1NT it is generally accepted that you need 15+ points and good stops in the opponents suit. So if your only 4+ suit is theirs and you have less than 15 points the decision should always be Pass and await events.
Doubling for Takeout should always show the values of an opening hand, theoretically 12+ but to safely Double with only 12/13 points you must be able to support all the other suits and so with obvious dangerous holdings such as a Doubleton in an unbid Major it is usually best to Pass or Overcall if you have 5 card suit
If partner is a passed hand and you have up to 14 points it is usually safer to overcall if you have a five card suit. Particularly if it is a Major as to Double and then bid your suit would normally should show a stronger hand.
With any hand of 15+ that you are unable to bid No Trumps you should make a Takeout Double