Step-by-step instructions are guides for getting up and running with a technique, such as How to export your emails from Gmail. They may include gifs, screenshots, and other media as needed to balance descriptiveness and brevity.
Quickstart instructions are also broken down into atomic steps, although these are specifically for getting up and running with a tool rather than a technique. An example would be Fix your password habit with Bitwarden on desktop. The goal of quickstarts is to be a quick resource, so there are likely to be fewer media like gifs and screenshots.
Templated instructions are intended as a starting point which you can use to think about and create your own processes. Some templates are basic, and some will be more detailed－depending on the goal of the instruction.