I don’t have a fat bike but I have a couple mountain bikes. I have a Trek Fuel EX 29er that I mounted 2.6” tires on. It’s not like those 4” tires but it is grippy. Regarding the night riding, I use two lights if riding a serious trail. I use a 1200 on the bars (2 beams) and a 700 on my helmet. With good lights, you will be able to see those limbs.