That’s not a layout currently available in Discourse, but it would be achievable through customization. It’s probably a bit complex for someone who’s new to Discourse to achieve — but you may be able to contract someone to build it for you in the marketplace category.
One of our default category layouts, “Categories with Featured Topics” is somewhat close to what you’re asking for, but it shows topics from all subcategories (rather than showing one per subcategory) and it’s also missing the poster details you’re asking for.
