Defaults arent allways the best. Installers show this in general unless you are a fan of bloatware.
Displacement wise its best to start at a power of 2. Its as minimalistic as possible and for that reason good. Once noticing the power 2 isnt capable of handling the requireed detail (or a random displacement bug shows up - where a non aligned displacement randomly would match a part of the power 3 displacement, but not on the power 2 - and suddenly projectiles go through the floor), only then should you go for power 3.
Also, if your disps go above 256 it can be 2 reasons: the path is too wide, or again it doesnt handle bumpyness.
Keep in mind that for a pathway 1024HU long you could use 2 power 3 displacements (efectivly mimicing 8 power 2), or 6 power 2 displacements for a somewhat similar effect. Yes, its slightly less detail, but thats exactly what the power 2 could be used for. And in this case, if a specific section would require additional detail, you might have gone for the power 4 on the left example, but for the right one a single power 3 might do well enough aswel.
The numbers on the image say how many spots can be edited on each side to explain the density a bit, the left example has 16 verticaly, and 8 horizontal, the right has 12 vertical and 8 horizontal.
Although for optimizing it isnt ideal, this situation allows adding detail later on much easier as its just clicking it up 1 power. And its very unlikely you would ever reach a power 4 that way.