I’d review https://github.com/CMB2/CMB2/wiki/Bringing-Metaboxes-to-the-Front-end and the Wiki in general which has a lot of good information on it.
Yes, I found this solution, but I would only be interested in rendering the field and use your plugin as a framework for generating different types of fields for custom forms, for example, registration form, contact form etc.
That part I don’t know so much about in regards to making use of CMB2 for. We’re not really a framework just to make form fields that you tie arbitrary things to, we’re generally specific for saving data to post/term/user meta and option pages.