First, why do you want a separate IP for each domain? There's very few reasons why you would need that. Anyway, no, a cPanel VPS would operate pretty much the same exact way in regards to add-on domains. Now, what you can do though, is get a cPanel reseller account with WHM access, then you can create individual cPanel accounts each with their own dedicated IPs. IPs are kind of expensive, and require justification, so just some things to think about.
VPS's are virtual private servers. For $6 a month, you'll get a linux VPS that won't have any control panel, no cPanel, or plesk. You'll just be doing things through the command line. Do you know how to install a web server, compile PHP, etc? That's what you'll have to do on a $6 VPS. Not to mention, keep up with kernel security updates.
cPanel and Plesk are both control panels, they sit on top of servers. VPS servers use a virtualization backend to run off of, that backend is not the same as cPanel/Plesk. VMware is an example of virtualization.
Your cheapest option would be to go with cPanel reseller hosting, that would give you the functionality you desire. A VPS wouldn't be good, because in addition to the $6 for the VPS, you'd spend $14 per month for the cPanel license, plus $25 per month for server management if you don't know how to do it.
I hope this helps point you in a direction.