Hypervisor questions

I plan to install Rockstor on my current HTPC rig. It has an i3-4560, 16GB RAM, 4x4TB HDD and GTX 660Ti. Moving the data is another story that I will tackle later.
Right now I want to know how I can learn more about Hypervisors and whether I should run Rockstor under KVM or ESXi.

And if I do choose one how will it work to see my drives.

I was under the impression that Rockstor had to be installed as the main drive but I kept seeing hypervisors on /r/homelab and did some research and seems like something of an option. Like I could run Mint and set Rockstor in ESXI on Mint with two cores. Then leave the 660ti in for whatever random thing I might want to do on Mint. I don't really want to use the 660ti as a shelf unit just yet. Before as an HTPC it was running windows and I was just playing some games on my tv. But now I want to make it a proper NAS/Server and doing so it doesn't really need a gpu when it is beside my router.

I am just confused with all the options. Probably going to be a couple weeks before I decide on a plan of action. And several more posts here. The only experience before I have is using Virtualbox to test out Linux Distros I might like. But Hypervisors are on hardware level so I don't know if I want to mess around with that on my main rig before deploying on the i3.

I would locate a random drive, and play around on whichever computer you prefer. In all reality, KVM vs ESXi is your choice, I personally like ESXi as it's less limited in terms of getting a Windows environment up and running.

Question: Is rockstor going to handle the array/RAID? If so you're going to have one hell of a time

Yeah I thought Rockstor would. But don't see how that would work if it wasn't the base system without some weird passthrough method.

Techincally in ESXi you should be able to pass drives into a VM, but this just has so many things wrong with it... Do you have any particular reasons for Rockstor over Freenas?

I don't like ZFS, rather go with BTRFS.