Pour over shows a grinder's flaws more plainly than any other method. The water moves slowly, so anything too fine turns the bed muddy and anything too coarse runs straight past. A grinder made for pour over is one that holds a medium setting cleanly.
Drawdown time is the tell. If the bed stalls there are too many fines. If the water rushes through, the grind is too coarse or too uneven.
Pour over is more forgiving than espresso on absolute fineness, and less forgiving of a wide spread. A handful of dust in an otherwise medium grind will slow the whole bed and pull bitterness with it.
For pour over the honest answer is that most people will not reliably taste the difference.
Conical burrs cover the filter range comfortably, run cooler and cost less. Flat burrs give a tighter distribution that shows up as clarity in light roasts — real, but subtle, and the last thing you should spend money on.
Get the brewing right first. The grinder difference is smaller than the pouring difference.
You want an adjustment that is readable and repeatable. A numbered dial you can return to is worth more day to day than a finer adjustment you cannot find again.
Stepped adjustment is perfectly adequate for filter. Stepless matters when you are chasing seconds on an espresso shot, not when you are pouring for three minutes.
If you switch between pour over and something coarser, check that the range covers both. Not every grinder does.
