My skillset is wide, with a strong blend of extensive experience and skills in web design, graphic design, visual identity, writing, blogging, branding, photography, audio and video production. Expert in all things Asana, Trello, and MailChimp, too:)
Teachable or Thinkific. Which one? Depends. You can read more here: https://www.webmatros.com/resources
Get Julie Dirksen's book Design for How People Learn – it's great and will help you with exactly that.
If by format you mean whether it should be video, an ebook, audiobook, etc – my best advice is to ask your audience, and look at which formats do best (competitors' competing products).