It just doesn't work on a second device until you stop the stream on the first device. Thats how it worked with my last 2 providers but may be different with others.
If it's not device locked your be fine
One tell tale sign that you're using 2 connections is that it becomes impossible to watch anything i.e constant buffer and freezing. its a way of telling you to close one and if you don't eventually one gets disconnected. Be careful though because if this happens frequently one of your devices might get permanently blocked
Mehhhh, there is no harm playing it on different devices 1 at a time. We certainly don't mind or hide it.
All the providers I've used when I turn it on a new device it interrupts and turns off the stream on the old device
They’ll notice, even if the service lets you open multiple streams.