We are working on integrations between GeneratePress theme styles and GenerateBlocks styles. For buttons this would be making it so GenerateBlocks buttons would use the Theme Button styles by default or possibly allow GB to style the theme buttons. Which is doable, but there are complications we have to overcome first.
For other HTML Input Elements such as fields, radio buttons, check boxes etc. that becomes more complicated, as the Theme does not output the HTML for them. They are generally added by another plugin or custom HTML. And they may have their own styles and classes the theme does not know about. If i can see them, i can advise 🙂