Fifty50 (free) gives you 2 blog layouts:
- Center
- List
For the pro version, you get the above plus an additional 4 blog layout styles:
- Grid (pro)
- Masonry(pro)
- Poster(pro)
- Minimal (pro)

By default, Fifty50 is installed with the Center layout chosen.

- Go to Appearance > Customize > Layout Options
- Look for the Blog Layout setting and make your choice from the dropdown list.
- Click the Publish button.