In French, les bonnes paroles means the good words. Not just any good words, not nice words, not pretty good words but the good words. The words that were good to say in the situation where they were used. Other words might also have been used and might have been good too. But these words were the good words.
Whenever anyone is told by someone about a recent death in their family, the listener will respond with good words. Some people seem to able to come up the good words to say under the circumstances.
That is best translated, in English, as the right words.
Whenever you see les bonnes/les bons/ la bonne/le bon you can feel free to assume it means the right.....
Juste carries a connotation of exactness.
The right words are those that are right for the exchange between you and me. The right words for a similar exchange between you and someone else might be different because of the difference in relationship.
Mot juste is more about the exact right words. Right for the situation not just right for the interaction. There are no other right words that can compare.
Of course most people will use the terms interchangeably.