Support height

I don't understand the support options in the various slicers. You can specify a z height gap which seems to default to less than one layer. How is that supposed to work?

I'm finding it difficult to tune the settings anyway. How do you set your support parameters?

Support structure needs to have a separation from actual print so you can remove it easily, so one layer separation is more than enough, less than that and you will suffer trying to remove it from the part. Then you have the infill and thickness (Simplify3d) don't know if other slicer have it but most likely they do. The thickness is basically the same as perimeters (how thick the support wall will be) and the infill establish how many support columns will be printed (100% will be a solid block).

The best way to learn is through experimentation, grab a hollow cube and put several on the built plate, then assign different support settings for each one and print them, find which setting works best for you. (Each part is unique, so the way you set the support changes with each part) .