In single page application, are you storing or generating the react js code in clientlib using front-end maven plugin? if not then I am not sure how you will use other components.
If I am not wrong, like in SPA the HTML generates from react developers and whatever they give you, you paste it to index.html.
if this is the case, using parsys is difficult. if not, you can use parsys in your spa page and then drag n drop the components.
~ Prince