Used to have a TB and there's no switch on it as I recall. It has two speakon outputs and a class D power amp.
Just connect your cabs either a speakon each or one speakon on the head and daisy chain on the cab. The amp adapts its power output accordingly.
It is not recommended to have a lower impedance than 4 Ohm as to not strain the transformer.
You can however safely run the amp without load, effectively running at infinite impedance.
I know the manual says otherwise, but that's a printing error.
I'm not sure about V1, but the second version definitely has a switch for speaker impedance.
Be sure to switch it to 4 ohms if you are using 2 eight ohm speakers.

