Chromecast query - Unregonised device iN Qobuz app

I assume Chromecast devices are wi-fi only, but may be wrong.

Concerned therefore to find a Chromecast 'Nearby device' in my Qobuz iPhone app in addition to the Nova.

If I turn off wi-fi but leave Bluetooth on both disappear.

So unless I'm seeing the Nova twice for some reason I'd  have to be concerned someone is accessing my LAN.

I have several original Amazon Echos and Echo Dots, don't think I can cast to those?

AppleTVs, PS4, Opp BluRay player are other connected devices apart from Macs.

Weird.