Can I change how my blog posts and blog page are laid out?

Yes. There are two template screens under Settings → Appearance:

• Blog Post Templates: the layout of each post, including the title, author, cover, content, share buttons, related posts and comments.
• Blog Listing Templates: the layout of the main blog page and every blog category and tag page.

They work like the other template screens:

1. Click Activate on a system template to switch to it, or Clone one to make your own copy.
2. Edit your copy, rearrange the blocks while watching the live preview, and click Save Layout.
3. Activate your copy to make it the store default.

If you haven't published a post yet, the post template preview uses a built-in sample post, so you can design the layout before you start writing.