Nope! Unlike some other tools which replace the native HUDs, MediaMate does not require tampering with SIP.
Yes! Download the app (with the button at the top of the page) and activate the Tryout Mode.
Of course! The Now Playing HUD displays information about the app that is outputting audio at that time. This can be a music service like Spotify, or even your favourite browser! Some apps (e.g. FireFox) might fail to display an album art when playing audio. Unfortunately, this is a limitation MediaMate cannot circumvent. If you notice an app that is unsupported and would like support, give me a heads up.
Currently not. However, basic support for apps like MonitorControl and Lunar (in Sync Mode) is included (but still in beta). Broader support might arrive in a future update.
Depending on how those other tools use the keys, there might be some problems of the two apps interfering with each other. If you enable "External App Support" in the app, those issues might be resolved. Give me a heads up if you notice issues with another app.
You can find more information on the app here.