I’ve drawn several flags using a vector illustration program, starting with the flag of Primosrky Krai (I should maybe fix that at some point in the future) and not least ending with a bunch of North Korean flags, with a square Union Jack somewhere in between. I like that flags are quite regular and usually geometrically well-defined; this element is so many percent of the hoist side length or the width of the flag. Construction guides make it easier but not easy enough, or folks just don’t have much experience with vector programs.
it’s a different way of looking at drawing, and I’m just afraid that I have no call or business to be doing anything other than vectors any more; raster programs frankly scare me.
It makes sense to look at most of these things using a gridded view, so that way things line up and make sense. On the other hand the SVG program of choice, Inkscape, liberally litters the code with bloat and nonstandard elements, but I’m not a programmer and I couldn’t tell you why that’s right, or important, or whether it’s what you really needed.