Thanks a lot for your kindness 
I am constrained by having to use Iomad theme because this distribution has plugins that only work with its theme or subthemes (I helped them to get it work with subthemes). So I can't use one of your excellent themes, at for example, choosing one that didn't have borders or rounded corners.
About subtheming, maybe I am misunderstanding. For what I understand, the page imports the parents themes and at last my subtheme. When they are compiled to css, each goes for their own. I mean, that if I change, as for example, color variables, I have to redeclare all the classes again to have those changes. Am I right?
The Iomad theme has not done much css, so most of the look comes from bootstrapbase. At the moment, I have copied all the bootstrapbase .less and file by file, I am deleting what is not border, color, shadow or round corner for importing in the main page. Then, I will apply the style for my subtheme. I hope you understand my bad English
))
Thanks a lot again and have a good day 