First off, don't refer to Euro cabinets as "Frameless" to your customers. Frameless implies something is missing.
Should you get a horizontal construction boring machine? Yes if you intend to assemble your cabinets with dowels. If you have the space and the work, get a case clamp as well.
You can build Euro cabinets with either Melamine, or plywood, Your preference. We usually use plywood for our sink base cabinets and melamine else where. But, it depends on the cabinet.
As for drawer guides, Blum seems to have taken over the market with their undermount and a dovetail drawer box. They are expensive, but its the market you serve that will determine the drawer box and guide. A set of Blum self closing undermount guides will cost over $25.
As for the varying over lap on the sides, you can do either, going to a thicker base plate, or going with a special application hinge. You will have to do some studying and learn the different applications. Your sales rep should be able to help you here as well.
I have been building Euro cabinets since 1987. Before that, I build faceframe cabinetry. I first think I notice with Euro was that I could build cabinets almost twice as fast. I do think installation is more difficult, the boxes can be racked out of square and that causes a problem. Most of the problems we encounter with Euro has to do with the installation. The cabinets need to be plumb and level.
As for the doors? No difference. As stated above, the industry allows for an 1/8" between the doors. However, you can do whatever you want. We make our doors 3/16" less than the door width. In our area, I found that with the 1/8" gap, sometimes the doors touched when we had high humidity. There is no "Gap Police", so do what works for you.
Regarding appliances, we usually build to the width and allow a space for above and below. We then fill in the space with a trim piece. Sometimes the literature is not clear and appliance manufactures reserve the right to make changes without any notice. On heavy appliances, like double ovens or even a heavy oven, we will install a cleat beneath the shelf holding the appliance. If we plan on a cleat, I will allow for a trim piece under the appliance so that there isn't any interference with a drawer under the oven.
We do about 90% Euro. Sometimes the designer will do both for the same job. Open cabinets usually have a frame applied over the box.