New to WP and want to get an official view on how headers should work. I'm using restarter plus as theme, but restarter seems to work the same, as do some other themes.
I want to use an image as my header for pages, about, etc. Initially, it didn't seem to work until I saw it turn up as part of a search result. After subsequent experimentation, I found that the header image shows on the post list page, but the feature image shows on individual pages. Odd since header image is specifically cropped to header size but feature image isn't.
Having found this, its not the end of the world as I can do what I want with a work around, but just want to make sure that I am not working around a bug or that I have missed an option - I notice on wordpress.org (https://wordpress.org/support/topic/header-changes-by-featured-image/) mention of an option, but its not there on restarter plus or free.
Am I right that individual posts and pages use the posts/page feature image, and that search results or posts lists use the header image?
Also, as a complete aside, is there any way that I can specify an image from a URL rather than medial library. I run two parallel sub domains, which as one are the same site, just logically separated for some features, but they share images, so just want to specify the single image from the server, rather than have to upload twice to the relevant subdomain media libraries.
Many thanks in advance