You can switch the screen that Parsec captures or the GPU that Parsec uses create the stream. Please use the Parsec Host settings to make that change.
SWITCH YOUR SCREEN OR GPU IN PARSEC
Parsec attempts to guess the right adapter (GPU) and monitor combination. Some computers, identify multiple adapters for one monitor. If you get error 15000, please switch the host adapter in the Host Settings area of Parsec and try to connect. You can also use this drop down to stream a different screen.
To apply the change, your client must disconnect and reconnect to the host.