My understanding would be:

• Probabilities: Chance of a certain outcome happening. E.g. Outcome A has a 70% chance B a 20% and C 10%

• Possibilities: what outcome scenarios exist. E.g. there exist 3 (A B C).

• Plausibility: looks at the degree of truth of a statement. So if it logically makes sense and is the correct answer/is what happened.

That reminds me of this Tom Scott video, which shares a somewhat similar idea.