The greater the magnification, the more important stability is -- just like with long lenses that magnify any motion -- but I've taken lots of high magnification shots from 35mm to 4x5" in the field on a Gitzo Reporter Performance without movement being an enormous problem. And most of the time I don't use flash.
And, as mentioned, if you want the same image on the film as the format increases, the magnification must be increased, but you won't have to enlarge nearly as much either to get the same print.
And, as mentioned, if you want the same image on the film as the format increases, the magnification must be increased, but you won't have to enlarge nearly as much either to get the same print.