As someone both relatively new to fatbiking (this is my 4th winter) and someone who spends as much time grooming winter trails as I do riding them, I feel compelled to chime in here.
First, it sounds like you've passed the rite of initiation to fat biking on snow. A veritable sufferfest with a few moments of salvation. This is normal.
Second, in line with your second revelation, fat biking on snow is extremely conditions dependent. I feel like my grooming informs how and when I ride and vice versa. Generally cold temperatures, low, gradual amounts of snowfall, and tons of tire traffic offer the best results. This isn't always the case but we had a good 2 months with maybe 5cm of snow total from Mid December to mid February and the trails were never better. The feeling of super densely packed firm snow and a great fat tire/rim combo is like nothing else, truly marvelous.
I'm not sure if I have a third specific point so I'll just share a few other thoughts:
- Brakes are important. Ideally you don't ever want to be riding in a situation where you have to control your speed by riding into deep, unpacked snow. I actually found running a 200mm rotor over the stock 160mm my Surly Wednesday came with, to be a marked improvement. Traction on snow is much more finite than on other surfaces so eventually you'll just lockout your tire and start sliding, risking a fall and damaging the trail surface. The larger rotor helps better modulate braking speed and power, resulting in a more confident and fine tuned feeling ride. Metallic pads are also important. Rotors get hot. You crash or go off trail, rotors get snowy, hot rotors melt snow and rotors get real wet.
- It's been said already but lose the tubes. Especially if you're headed to Baja.
- Fatbike forks can be fun. I use a Rockshox bluto and it actually weighs less than the stock surly fork. It's not a good fork in the summer but for smooth winter trail it's a blast and noticeably more comfortable than the rigid option. Just be sure to use winter seals and check air pressure before riding. I've had zero issues down to -35 C
All in all, fat bikes are a bit bizarre and they can vary greatly, even within a category that seems so niche. That said, they are amazing tools for exploration and off season riding fun. I'm fortunate enough to live in a place (The Yukon) that has an abundance of trail suited to winter riding and grooming. Additionally, we've got tons of backcountry snow machine and dogsled trails that get put in over the course of the winter. Mixing machine groomed trail with backcountry packed trail and frozen waterways provides opportunity to explore routes that don't exist in the summer. Good luck with getting the bike dialed in to your desires and have fun!