Now you can use No/None module instead of the Universal Module since you can create text field configurable options, but if asking for a domain or anything the Universal Module is probably better.
I'd personally use the Universal Module it worked for me when I sold integrations and did them as a service.
That depends on who you're buying from or the control panel you'll be using.
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Awesome plugin, works reliably and really very useful!
As much as it's good to support other panels I don't think CWP should be one that's implemented, in terms of control panels it's an absolute train wreck. I would think that cPanel and then Plesk down the line would be sufficient.