I believe that minoxidil studies were only completed on the crown and therefore they could only state that minoxidil was effective in those areas, when in reality minoxidil is also helpful for the hairline. In terms of brands, imo there's no real difference between the brands in terms of effectiveness and simply some are greasier, some dry quicker etc.
Personally, I use Kirkland foam in the morning since it dries quickly and leaves no residue. I then use Lipogaine liquid at night as its greasy as hell but who cares because I wait 30-60mins and then go to sleep. I'm thinking of switching to Kirkland liquid at night, since the cost is a third of Lipogaine and I don't think Lipo can justify the cost.