Does the resistor divider value used in adjustable linear regulators matter? If so, to what extent
A lower resistance will result in a higher wasted power which will require a higher wattage rating in the resistors. Too high a resistance and you may have issues with tolerance, and too high a resistance in parallel with the high Impedance input of the feedback pin can result in the resulting voltage being wrong.

The input is often one side of an op amp or comparator block.