On point 1, there is also a cost to doing registration on large scale stuff. I have the XL Axidraw and am limited to 11" x 17" so if I want to go bigger I have to set up registration marks and make sure they're aligned.
Only for that style of machine, I think (not entirely sure what you mean). Flatbed or large format (paper drapes down each side and gets moved back and forth) plotters don't have that requirement. My A2 flatbed holds the paper in place electrostatically, and nothing can move once that's switched on; you position it where you want and press a button, then smooth it down. The Axidraw style plotters seem quite limited in comparison (and the cheap ones very imprecise).
I'm not visualizing what you have but having the bed static certainly makes sense. But any plotter where the tool moves and not the source will have this issue.
If the plotter is big enough to hold the whole piece of paper (or move the paper through on its own) there is no registration to worry about, and flatbed and large-format plotters do that.
Right, that's (the vinyl cutter variety) not wildly different than the Cricut (which I mentioned before, and can also pen plot)
I guess I'm thinking larger than 17" and the two flatbed ones you linked would suffer from the same problem (except that the first probably has no way to do larger than its bed)
