If DC then yes no triacs, was unsure, and I have seen a lot of pinball machines that just used the AC for things.
As to the +-20V gate rating, this is because the gate has a very thin oxide layer, which is part of the design and why it works. You limit the voltage to 20V WRT the sorce, as the mosfet will turn on with a positive voltage over the threshold voltage, and a negative voltage will help it turn off faster if needed. In you application this is not needed, but is used sometimes.
As well you get P channel devices, which need a negative voltage to switch. You also get depletion mode devices, which are normally on and where the voltage applied turns them off, but they are not common and are not really high power devices.