If you are using Responsive Web Design, use meta name="viewport" tag to tell the browser how to adjust the content. If you use Dynamic Serving, use the Vary HTTP header to signal your changes depending on the user-agent. If you are using separate URLs, signal the relationship between two URLs by tag with rel="canonical" and rel="alternate" elements.
It appears that the reason this page from a little-known website is able to rank amongst the bigger players is that the content itself is more focussed. It talks about how to name images for SEO, whereas most of the other pages are more general guides to image SEO—which all presumably mention the importance of naming images correctly, amongst other things.
Paid search results are those in the top and bottom of the results page, indicated by the small “ad” icon. These are placements that businesses pay for to show up when users search specific keywords. Google Ads can be a very effective way of utilizing ad spend for those who are new or struggling to compete against businesses that rank higher in organic search results. It’s also great for businesses targeting keywords with high revenue potential.