Don’t try it on a workspace with live devices. It pauses every running flow on every host, root flows included, and the root flow is the one storing your device data. Device messages, schedules and webhooks start no run until you resume.
It does ask first: you tick “I understand that nothing runs until the flows are resumed.” and type STOP. Resume the flows brings back every flow the stop paused. A flow that had paused itself before stays paused. Both are in the audit log.