How to customize a template in Astra child theme?

We have a website that’s using the Astra theme. Our website has a blog (but also other pages).

I don’t like the layout of the blog page. Specifically there is no H1 heading, featured images are shown full-size (so the page is mostly huge images) and it’s really not user friendly. There are no customization options available within the theme to fix these issues.

So, I created a child theme using the Astra child theme generator, hoping I could just create my own blog template to use. I thought I would copy theirs as a starting point, but I can’t tell if it’s using archive.php or index.php or something else, and it’s using custom methods like “astra_content_loop()” which I can’t find where they are defined.

Has anyone done anything like this before who can help me get started customizing the blog index page? I do have web programming experience, just not with WP themes.

I would like to:
– add a heading and possibly a text blurb to the page that can be edited in WP
– customize the featured image to be a thumbnail instead of full-size
– if possible, change the layout to be more attractive