General questions regarding whether certain plugins are necessary and correct setup procedure

I have several questions that I would like to ask about whether certain plugins are necessary to achieve my network setup.

I am running a multisite WP4 with dedicated IP hosting environment and would like to discuss the relevance as well as pros and cons of using a combination of you plugins to setup a full blown CMS system and hosting network selling domain names, hosting, and premium services and add-ons.

Once the best solution and combination of your plugins has been identified I want to establish the correct procedural steps for setting up the plugins as some of them are not straight forward installs and require certain system side modifications to be carried out first in a particular order.

It would be grateful if I could have a direct conversation with one of your support experts with whom I can grant access to my network setup via "support access" to ensure that everything is completed without error.

I am also considering signing up for WHMCS and would like to take your advice on whether this is the best route for me or whether I maintain my own Pro Site hosting setup.

The plugins in concern are:

Pro Sites
Domain Mapping

WHMCS WP Integration?
WHMCS MU Provisioning?