Yes, this is probably the correct approach for your case. For details about setting this up, have a look at the video in this topic: [Video] How to create a private category using group permissions.
Another feature that is available to groups is that personal messages can be sent to all group members. This is especially useful for customer support type scenarios.
It’s hard to know what the best approach would be for your case, but managing group memberships, payments, and commissions from WordPress would definitely be possible. This would be easiest to do if your WordPress site is the SSO provider for your Discourse site. Our WordPress plugin can be used to enable SSO between WordPress and Discourse. It also makes a few functions available that can be used by developers for managing Discourse group membership.
If you are using the WP DIscourse plugin with Woocommerce, you may need to install https://github.com/scossar/wp-discourse-woocommerce-support. An alternative to installing that plugin is to just add the functions given in the plugin’s README to your site.