it will save you manually editing/updating each page if you want to change some in the future.
For the Element page header/hero section. Not really a best practice, as long as it contains the anything necessary for your SEO eg. a H1 for the title, then you should be good to go.
You need to set the Display Rules Locations so it only applies to the pages or posts that you want it to.
There are some general locations such as Pages -> All Pages or Posts -> All Posts or All Archives
Where possible its best to stick to these general rules. And avoid having a lost list of specific pages or posts.