How will this affect my ability to analyze traffic on my site? Can I still use the analytics plug-in I have installed on my WP instance (I suppose not?) or will I have to manage those inside the Frontity project somehow (like shipping Google analytics scripts with the client-side js)?
The analytics script should be installed in the React theme. We plan to release a Google Analytics extension so you will only have to configure it with your GA ID. But the plugin you are using right now will not work anymore, with Frontity your WordPress becomes the source of data for your site (like a headless CMS) and the frontend is totally decoupled from the backend.