I do not load for the 45-70, but I do load for other straight walled cases. The same principals apply. For a straight case, you usually have 3 dies. 1 is the sizer/decapping die. 2 is the expander die and 3 is the bullet seating and cripping die. I run the case all the way into the size die. I then run the case into the case mouth expansion die for cast bullets, I skip it for jacketed bullets ( I just make sure the case mouths have an inside chamfer). I then seat the bullet and have the crimping part adjusted so there is a light crimp. This needs to be adjusted from bullet to bullet, because they are all different in length. In some cases, I have made special plugs for odd shaped bullets. Most companies will make custom plugs for a small fee, if you send them a bullet or two for samples. Some die sets separate the crimp from the bullet seater. Most bullet plugs are made for a flat point bullet (straight walled) or a pointed bullet (bottle necked). If you use a pointed bullet with a bullet seater made for a flat pointed bullet, you will need to make a change or flatten out the point. If you are using a round point bullet with a flat point plug, you may deform the point a little, but not enough to hurt anything.
You were asking about the 45-70, which is a straight walled case. To me this is pretty straight forward as I have described. If you get into bottle necked cases, then the process is much more varied. Depending on what I am loading and what it will be used for. I use a vast array of die types from full length sizers, neck sizers, collet sizers and bushing neck sizers. I even have a full length sizer with a bushing neck sizer. I also have a Lyman type "M" die to straighten out necks that are dented for any .224 size case mouth. That is just doing sizing, bullet seating is a whole 'nother set of dies and ways of doing it. "Rifle" dies usually come in two die sets, but some times deluxe sets will have an extra die or two in the set. Or you can put together your own set from different manufacturer's.
Good Luck and Good Shooting