The whole subject of how to connect a mixer & sound card to a computer running PlayIt Live and then streaming the output seems to cause some confusion.
This is intended to be a simple "how to" which can be adapted as required.
I've used a basic three channel mixer which I had to hand. The first channel is Mic/Line, the other two can do phono or line.
In this case I've got line inputs connected to all three channels (from a three stereo channel sound card) and the mixer output connected back into the computer.
The sound card is another spare I had to hand, a Hercules Deejay Trim 4 & 6.
This has three stereo outputs. I could only get these to work using ASIO (the driver should support the normal windows sound system as well but didn't seem to under Windows 10).
It would have been better to use the USB sound card but that didn't seem to be recognised as in input on the computer correctly.
Having got the hardware connected I started PlayIt Live and configured the outputs.
The mixer only has three stereo inputs connected to faders (one shared with the microphone) so there were some compromises.
The "better" outputs of the sound card (with output indication meters) are 1/2 & 3/4 so I allocated them to two players and connected those to the second and third mixer faders.
Finally, the input from the mixer was selected as the Audio Source to broadcast and the relevant output on the mixer and PC levels set to give a reasonable level on music.
A slightly random selection of music was going to play for the next hour or so.
Assuming the microphone connects to the mixer (so connects via a microphone plug into a mixer channel), no.
In the example above the microphone is on the first channel of the mixer and PlayIt Live appears on channels 2 & 3.
You only need the microphone plug in if your microphone has a USB connection and plugs into the computer.