I am neither strong, fast or fit and I ride (rode) SS. 32×16 FWIW.
I mostly ride alone, generally riding what used to be called XC or “dicking about in the woods”. Linking little bits of trail up I can about manage 25 miles from my house and back again. I tend to walk up steep hills with a geared bike and tend to wear myself out more by trying to be fast. I must confess to having gears on currently as trail centres with mates were getting a bit dull as I’d have to sprint past them on the climbs (you can’t just spin up) and they’d leave me standing on the long draggy fire roads.
I still ride SS on the road and find that generally (top speed aside) I’m faster as I’m trying harder!
Weirdly SS MTB reminds me of riding BMX, in the way we used to park on the industrial estates on the outskirts of nottingham and then slowly ride into the city, jumping, grinding, manualling off everything we could. Its kind of a fun way to ride, but I probably wouldn’t attempt an all day epic SS. (though I have done road sportives SS)