I have set up a test site. It is only the first, main site. This site has been running since version 3.2 or so.
I can have this plugin run on the main site, and use Limit to Stores to the first one. Then can use another on the second.
Or I can use this one as a multi site.
Looking at dev tools when the request comes back, it has the token and payerId. Just on the first site, it routes to an empty cart.