Eh, some flex in there, but 'plus' is ~2.8-3.x, 'fat' are somewhere high 3.x on up. Personally I consider anything 3.8-4.0" or wider as fat tires.What size tyres in fat category? Burn Rubber Robbie.!!!!
As far as the 'what do you hate,' I never had any self-steering on my juggernaut 4.0" fat tire bike, but I rented an M500 overseas with 4.2-4.4" wide tires, and definitely felt some self-steering. Wasn't terrible but also wasn't super pleasant when it happened. Didn't have a pump to see if could correct via pressure, though.