At this point, for me Django is pretty much synonymous with Django REST framework (https://www.django-rest-framework.org/). I can't imagine a better API than Django w/ REST framework.
For static sites I use Django's templates. Otherwise, I just use Django w/ REST framework for my API, and to serve up index.html. My index.html will include a link to my JS bundle(s) - I use a separate build system (Webpack/Babel/etc) to handle JS.