The Opinion theme provides quite a few different layouts for post listings which you can fully manage and tweak to your needs, then choose to display them on Home (modules) page or any archive template later. To manage the layout options, go to Theme Options -> Post Layouts.
Each of the layouts has very similar display options, like choosing whether you want to display category link, metadata, a text excerpt, etc… Below is an example of Layout A settings.
On all archive pages as well as in modules (described later), you will find the option to choose one or more available layout sets.
Note: Changing an image ratio
Whenever you change an image ratio for a specific post layout, please make sure that you run Force Regenerate Thumbnails plugin afterward, as WordPress needs to recreate images based on the new dimensions you specified.