a handy guide somewhere that lists all the different variations of bitcoin that are out there?
Here is one
https://www.forks.net/list/Bitcoin//1/2017-01-01/2020-01-01 But I assume there are many more forks of it. It just wasn't so popular until previous year. For example if I am not wrong I think also Litecoin is a fork from BTC and many others. Just search google if you want to find better list of forks.
But don't bother to much with this forks, practically anyone can make it's own copy, meaning it's worthless unless some kind of consensus develops around a coin (miners, trades, users, holders, devs etc.)
There is only one Bitcoin and this is Bitcoin.
Bitcoin core is a software, not network.
Bitcoin Core is an implementation of bitcoin. Initially, the software was published by Satoshi Nakamoto under the name "Bitcoin", and later renamed to "Bitcoin Core" to distinguish it from the network.
Source:
https://en.wikipedia.org/wiki/Bitcoin_Core.
If I want to purchase "Bitcoin Cash" I am supposed to purchase the ticker "BCH", that much I have figured out. If someone wanted to invest in the original bitcoin vision of the "Satoshi Nakamoto" person(a), which symbol am I buying? What if I want to purchase the vision of the folks who want to modify the original bitcoin which I understand is called "Bitcoin Core". Which of these am I buying when I am buying "BTC", and what is the ticker for the other version?
bitcoin = BTC (original blockchain)
bitcoin cash = BCH (the forked one)
I don't know where your confusion comes from.