It's + plural noun
This is a matter of usage rather than numerical agreement.
With “it’s the decisions”, the word decisions is used in the abstract. It doesn’t refer to any particular decision.
When you say “they’re the decisions”, the word decisions refers to a specific set of decisions.
So “it’s the decisions you should make” is an exhortation to make decisions, while “they’re the decisions you should make” urges the adoption of a specific set of decisions.