I will say that having adjustable damping on the fly is really, really nice. You can tune the shock as you go for different road surfaces, passenger weight, etc.
I put a lot of miles on my regular ride and it has their remote adjuster and it’s spring for riding weight. I spent a bit of time tuning the slow and high speed compression. Now, I crank the knob + or - depending upon riding condition to get a consistent ride (the low and high speed remains proportional). Highway, I go less, backroads at more aggressive speeds, I tighten her up. Priceless.
The length I would base off your trail objective then go with a calculated weight spring setup. Best $ I’ve ever spent on improving the performance of a bike.
My opinions...