I read somewhere in a suspension book years ago that when you cut a spring to lower ride height you actual increase the spring rate. didn't really make sense to me even thou they spent pages explaining it lol but the idea was basically if you're going to lower your car you need springs at a different rate and length to end up in the same place.
that's engineer level stuff thou, we just have to work with what we can find that fits our car/truck. but if given the option I've found lowering springs wound Progressive give the best ride. long long time ago i replaced the stock springs on a firebird with some expensive for the time progressive eibach springs. car sat little over an inch lower but rode much nicer. big bumps still sucked but the small washboard ones felt way smoother.
no clue if they even make that stuff anymore or for these trucks. just saying.
my other chase for a nice ride is this c6 corvette. it had the z51 suspension and rode like a brick stock and on anything but the smoothest road would skitter across the road in corners. over all horrible driving experience for me.. but I know others that love it because race car. to me it meant slow car and lots of active handling to try and cover for garage setup that probably only worked in autocross setup where you do 30mph and yank the wheel left and right. (I despise autocross lol)
anyways, the stock fiberglass leaf spring has some progress rate to it. all coilovers that fit it do not. I've been in 3 with different brands of coilovers, I'm sure they have their place in racing and tuning easily for it. but they were all horrible. adjust soft they got bounce with no control, stiffen them up they rode like a slammed Honda. the vikings were the worst. noisey as hell too, but in a odd way. I was told it was the valves in the shock seating and unsesting in each direction. they also do away with any rubber bushings so you hear everything. I've not been around $10k sets but eh.. going to say not for bad roads and long road trips.
so far best I've found was keep the stiffer z51 leaf springs for the progressive rate, and koni makes a passive 2 rate shock. short fast wash board its very low damping, slower big compression switch to a different channel and have high damping but still less than the stock z51 shocks. this allows for some weight transfer and shifting it around when driving so got tons of rear traction back, especially when the road isn't perfect. get on throttle a ton earlier, and can actually drive the car without all the electronics on to save you..but down side to them you need to have enough travel, so stock or close to it ride height.
to compensate for the stock monster truck fender gap, you gotta go bigger with tire size to fill the gap. which isn't that bad cause more contact patch. I'm not sure if koni makes the shocks that would fit your lowered truck. but if so, highly recommend. KONI FSD is what they are called. might give their tech line a call.
I say all that to just basically say in my experience progressive coil springs with high quality dampers tuned to what you're looking for goes a long way towards a nicer ride. don't cheap out on shocks and talk to the tech lines and be sure to tell them ride ride ride. handling will come from the wheel/tire and thick sway bars setup in anything close to street speeds. if you tried to do track days in it or chase down Porsches on the mountain roads. you'd have to give some of that up.