Hellava lot as it happens. The primary consideration is what the home owners actually like and what will work in their area/zone.
Next comes the ideas and the mock up of several plans. This includes several 3D sketches. How else is the home owner going to know what the prospective designs look like? Not from an overhead. Overheads only work when the owner knows the product and can envisage the outcome.
Getting something that works means everyone pulls together. The product has to be right for the location and also for the home owner. Bottom line is he who pays the piper calls the tune.
This is a labor of love