I ride fixed on-road, and single off, but fixed off road seems madness. You’ll just be smashing your pedals into stuff all the time I reckon.
It is.
You learn to ride through the stuff you’ve smashed into quite rapidly :0)
My typical SS gear was 32:17 but always ran 32:16 fixed which seemed to work out fine. Bit more grunt climbing and a bit more speed on the flat and downhill. (or less manic spinning)
Depending on where you ride I’d go with 2 brakes if you can. Will give your wrecked legs a chance on long downhills and in the mud if the front lets go under heavy braking your basically out of braking without a rear brake as your legs can’t do the fine adjustment.
I found a pair of V brakes was superior to a single front disk brake in winter.