When starting a new company and building a new product w/ limited engineering we chose to optimize for expertise and rapid development, landing on Rails API, w/ AngularJS on the front.
The reality is that we're building a CRUD app, so we considered going w/ vanilla Rails MVC to optimize velocity early on (it may not be sexy, but it gets the job done). Instead, we opted to split the codebase to allow for a richer front-end experience, focus on skill specificity when hiring, and give us the flexibility to be consumed by multiple clients in the future.
We also considered .NET core or Node.js for the API layer, and React on the front-end, but our experiences dealing with mature Node APIs and the rapid-fire changes that comes with state management in React-land put us off, given our level of experience with those tools.
We're using GitHub and Trello to track issues and projects, and a plethora of other tools to help the operational team, like Zapier, MailChimp, Google Drive with some basic Vue.js & HTML5 apps for smaller internal-facing web projects.