You seem to be asking a few things here.
In terms of how you should be hosting: depending on your goals, Amazon Web Services may be a little more than you're looking for at the moment. If you're just getting started with web hosting and deployment I would highly recommend taking a look at something more straightforward(and free!) such as Heroku. This might help you get a grasp on the process of deployment, and they have a decent getting started guide specifically for node.
That said, if you are certain you'd like to dive in with Amazon Web Services there are several different services available to choose from (including lightsail) that you also may want to consider before continuing.
And finally to answer your main question: Yes, if you choose an Ubuntu distro for an OS you will indeed be able to install npm, node, and all the packages you'll require for your app (likely via a command line interface). I am not personally familiar with the specifics of Lightsail, but they have their own getting started guide you might want to read through for linux setups.