Do you have data that allows you to objectively measure your team’s effectiveness as well as any positive impacts? What data do you currently rely on?

Suggest multiple data points. We have incident data, time to respond and time to resolve as one set. We can't stop all incidents (so that alone is misleading) and when we have more the time to resolve is expected to extend. As far as the delivery of improvements I use OKR's e.g. Objective: Increase Efficiency, Key Result: % automated controls, % advisory findings vs assurance findings.

Yes, we use Jira, JiraAlign and BI to measure team KPIs and effectiveness