I see this question a lot as it relates to the MPCNC, where I spend most of my time helping people. So this is sort of from that perspective, where things are heavier and Z movements are larger, as you plunge into material.
Regarding backlash, as long as the bed is free to move, there should be basically none. The bed is heavy enough, and the plastic/nozzle is pushing down, not pulling up, so it should always stay at the lowest spot regarding backlash.
For the same torque on the screw, the 1 start should have 4x the force pushing or pulling. But it will move 4x slower for the same motor shaft speed.
If you try to move the bed at 15mm/s with a 4 start, the motor shaft is moving 4x slower than 15mm/s with a 1 start.
Stepper motors have the most torque when they are moving slower, so as you go faster, they will have less torque. If the friction and the weight of the bed are greater than the torque, it will skip steps. I think that is a 10x bigger issue in CNC than in 3D printing. Most of the Z moves in 3D printing are so small, there isn’t any speed that would matter, except when homing.
A 24V supply doesn’t give you any more torque at lower speeds, but it does increase the speed where you really lose torque. So it is probably not a huge deal.
You can set the homing speed slower in the Marlin configuration. You can also just set the max Z feedrate with a Gcode (M204, I think?). It can also be set in the slicer.