I own a fat bike and love it for its intended purpose, but if you are riding it on the road - even dirt road or bike path / rail-to-trail - it is really a poor choice. You basically get all the drawbacks of a fat bike without being able to make use of the benefits.
The main drawback is that a 4-5” wide tire and a 80-100mm rim is freaking HEAVY. Your talking 2-3 lbs extra per wheel compared to a gravel bike running 32-38mm tires. And this is in the one place that weight hurts the most.
And for all that weight you get a bunch of floatation and the ability to run insanely low pressures. Niether of which do you any good on the road.