There are three primary screen mirroring security risks that you should make sure to address when evaluating a wireless screen mirroring system for your business meeting and conference rooms: Unauthorized network access. Unauthorized content access. No manufacturer support.

Can screen mirroring be detected?

You can't detect but you can remove functionality which mirrors. No software can mirror if developer option is disabled.

Is screen mirroring bad for phone?

No such thing. Their is no issue in casting videos. Your screen might be getting warm after 20-30 minutes of videos ..which is absolutely normal.