Documentation on Template files

I’m using the Avada theme and working to add a LifterLMS course, however, the theme must not be well coded because the video player doesn’t respect the content box (having hard coded properties) and I’d also like to change how the feature image is displayed, well the whole formatting frankly.
What I’d really like to know is where the templates are pulled from to create the HTML I see on the page. Yes, I’ve dug into the code and read through the docs but I can’t seem to find the info I need.
Thanks for any and all help in pointing me in the right direction.