is better with restric content pro. Much more simple plugin and the purpose of the plugin is the one you are looking for.
as RCP do not work with multisite, you have to use the site 1 as the place for the payment and later to use https://es.wordpress.org/plugins/multisite-user-role-sync/ or https://es.wordpress.org/plugins/multisite-user-sync/ or a simmilar tool to allow to have the same user with the same role in all the subsites.
The idea is. The user pay in site 1. So, we have to create the same role in all the subsites. And each time in site 1 the role change (from visitor to subscriber), the role in each sub site must change too.
RCP can work with subscription levels, but we have the use the role way of restriction. Otherwise, do not works.
i can tell you the details if you wish. That is our working way.