Great to hear, Chris. Welcome to the community and looking forward to collaborating with you.
Github is the best place for development discussions - there are many issues that could use some love, as well as PRs that need to be reviewed/patched. As a general rule, the core team members tend to concentrate on what's closer to their needs/heart/expertise, so there is no set of priorities. Feel free to bump issues that you would want to work on.
As far as the plugin development goes, you would be making everyone a favor by making sure your plugins are compatible with composer and are registered on packagist. It will make installing and updating plugins a lot easier.
Security issues should be reported to firstname.lastname@example.org!