Is Creatine good for muscle & strength?

Yes — the evidence for this is strong. Creatine supplementation combined with resistance training consistently increases muscle strength and mass across multiple independent meta-analyses, including specifically in older adults and postmenopausal women, and improves upper-body and lower-body strength and power. That's reflected in an evidence score of 88/100 for its role in muscle & strength, drawn from 11 studies, with an estimated impact on longevity rated substantial (68/100).