We suggest you create the child theme for the modification on the theme. If you update the theme in future updates then it will replace the codes that you have added.
Everyone who want to add bootstrap design, ‘ll do it, as there are a lot courses. One of them “TutsPlus – Building WordPress Themes With Bootstrap”.
But another way, seo mistakes in template – those require code directly editing. h1 – in head, h2 – in body title and etc. And every update ‘ll return code customization back by default. I suppose that is not flexible and fixible. Just do all customization lock it for update, and use it.