Share HTML page, Mobile Responsive, Live Preview

I am going to use the CMS for the first time. This is a naive question. For the following features, what do I need to do? Can this be achieved using Strapi or do I need something like Gatsby or NextJS?

  • Ability to share an HTML page with my Partner(s) so that they can simply copy it on their site.
  • Mobile Responsive site
  • Preview before making it live
  • Themes: Ability to customise almost everything like Buttons, Typography, …