Hi Justin,

You're mostly right - Salesforce uses Javascript for it's Lightning Components, however at least Apex is also commonly used as a part of Lightning-related development tasks, so you'll somehow touch it for sure.

In general, Salesforce uses it's own Aura framework for building Lightning components and Applications and you're not able to use any "complex" frameworks like AngularJS or NodeJS, however you still can work with jQuery or similar frameworks (or, maybe, better to call it library). I don't think that I can recommend anything in this direction as it solely depends on the project you are working on. The Welkin Suite provides a general code completion for Javascript without additional features for frameworks, however during this summer we will improve our Javascript code completion and will add more Aura-specific features to the Lightning editor.

Thank you,

Vladimir