1
Identify the actual risk
Decide whether safe means protection from unauthorized access, limits on data retention, permission to process a client's recording or confidence in transcript accuracy. These are different questions, and an answer to one does not settle the others.
2
Match claims to current terms
Look for dated, first-party information covering the service and deployment you intend to use. Check data handling, deletion, subprocessors and available agreements; if a point is unclear, ask the provider rather than filling the gap with a Reddit comment.
3
Test with appropriate material
Start with non-sensitive audio you have the right to process. Record what you submit, what output you receive and which settings or contractual terms apply before considering confidential calls, personal information or regulated material.