-It will be no collisions and necessarily not any cutting air if just making holes.
-Yes regions will reduce this and you can also use clipping planes for reducing the height and depth of the toolpath.
-Yes you can use region curves in the entry level and in the four axis version of madCAM.
- It depends on how complex the model is.
-If cutting a casting, it is possible to use the “stock to leave” and cut in two or more steps.
-It saves time and creates a toolpath that doesn’t cut in the air because the user defined stock model is a 3-dimmensional region. On simple parts when just cutting some holes, it won’t make much of an advantage.