Hi, @storton - great choice to look around for a better developer experience! Notepad++ will always have its place on every developer’s Windows machine, but there are certainly popular IDEs and editors with rich integrations that are a pleasure to explore and work with.
The single most popular IDE in the PHP (and Symfony (and therefore eZ Platform)) world is PhpStorm. It’s not free, but there’s a trial version you can use to check it out and try-before-you-buy. You can go to Preferences -> Plugins, search for “ez”, and if the plugin is not found then click “Search in repositories” to locate and install an unofficial plugin for PhpStorm.
While they do add a lot of value in their commercial product, you can still enjoy a free Community Edition called “IntelliJ IDEA CE” and install a smaller subset of plugins to achieve your goals. Another free option that I have used for PHP projects for many years is the NetBeans IDE, which offers excellent PHP support.
Atom is a great text editor, and there are many fine plugins for editing in general. You are not likely to find eZ-specific plugins outside of the PhpStorm unofficial plugin mentioned above, but with proper indexing and either Symfony or just plain PHP support, many IDEs and editors are smart enough to build a model of your project and suggest things with various degrees of relevance.
Some other nice editors include Microsoft’s fork of Atom called VisualStudio Code, Sublime, as well as several smaller contenders. There are other IDEs as well, such as Aptana, Komodo, and more.
There are even online editors such as c9.io that are starting to have quite a strong set of features.
I’m personally content to use Emacs, Atom, and NetBeans for my personal projects, and I do use my PhpStorm license for work projects to stay comfortable working in the most popular IDE in the PHP world today. I recommend trying everything and deciding on your favorites. Even experiencing the ones you won’t use in the future enriches your appreciation for the ones you will.