Welcome to TurnKey. Thanks for posting! Especially when it doesn't "just make sense" to you. Clearly there is some "curse of knowledge" going on here...

The first resource I'd point you to is a wiki page that a new user made a number of years ago: New to TurnKey? Overview in links. It is quite dated, but I've just spent the last hour or so going through it to bring it up to date. It's likely I've missed stuff, but it should be close! Most of the info is somewhat historical and/or fundamental in nature anyway so should generally be still relevant. I'm pretty sure that I've updated all the technical detail.

Hopefully that will be useful?! Although it is mostly words. If any of it doesn't make sense or you'd like elaboration on, please feel free to ask. Perhaps we should have a page for definitions of common jargon or something?

To respond to a couple of your specific points:

My assumption with turnkey was "get the iso, install on bare metal, do setup stuff like usual"

You could do that and it should (fingers crossed) Just work!

But personally, I wouldn't.

My first reason is because IMO it's almost always a waste of resources. I run tons of VMs on some pretty minimalist hardware by today's standards. The only spec that's likely better than your average PC is that it has 32GB RAM. Even if you only plan to run one server, I still think it's still better running as a VM on a hypervisor. TBH, personally I don't think that a server workload really ever deserves to run on bare metal hardware. The additional flexibility you get running as a VM more than makes up for the tiny bit of overhead you get from the hypervisor IMO - although obviously that depends on the hypervisor.

Personally my favorite hypervisor (and the one I use myself) is ProxmoxVE. We actually have a partnership with them and our appliances are available for download within the web UI. On Proxmox you can install to a "proper" VM from ISO, or you can download a LXC template and run it as a container. (FYI containers are a low overhead way to run linux on linux). Generally containers run as if they were on bare metal (relative to resources you allocate) - so are perfect for ensuring that you're wasting as few resources as possible.

But each to their own... I'm sure there are scenarios where a bare metal install makes the most sense. And if it's what you want to do, why the hell not? We're certainly not stopping you - at least not intentionally.

The other reason is that unfortunately, whilst in theory you can install to bare metal from ISO, the hardware support is pretty sad. It only support legacy BIOS (no UEFI support) so isn't great for newer hardware. It also doesn't include non-free drivers, so you may need to manually install drivers via a USB (which I'd be more than happy to help you with if that's a problem).

IMO there is something of a chicken and egg issue. Our installer doesn't have great hardware support, so we don't have many users running on bare metal. Those that do, our existing set up "just works", those that try and fail, usually wander off somewhere else. Then, because we don't have many users running on bare metal (or wanting to run on bare metal), there's not much incentive for us to prioritise hardware support. Especially when all of our revenue comes from running on AWS (which is basically just a giant hypervisor cluster).

I'm used to using Fedora

FYI, TurnKey is based on Debian.

I would like the entire system to be available to the servers just in case it's needed, and I seriously have no idea what I'm doing anymore.

See my note above about installing to bare metal if you wish.

Although I would encourage you to consider LXC. Unless your server is particularly low power, has crazy high resource requirements and/or is dealing with huge volumes of traffic, it seems like just making life harder for yourself to save a few MB and a few CPU cycles (which you likely wouldn't even notice under LXC).

In fairness, my IT knowledge has really been in the VM space for many years now. And I've seen it go from novelty idea, to the best way to do things (IMO). My very first taste of it was when I moved a bare metal Windows server install to a VM on Proxmox (same hardware - except for the HDD). I'm not sure why but it ran so much better as a VM than it had on hardware (on the same hardware!). I was sold and have never looked back.

Quickly cloning a server to test something out (with zero downtime), retiring a server and replacing it with something completely different, testing different distros or services side-by-side, adjusting resources on the fly, the list goes on.

Regarldess, as I noted above, if you want to run on bare metal, give it a go. Hopefully it might work for you? If not, please feel fre to report issues and I'll help where I can. Although UEFI support (and therefore safeboot too) is currently a hard no.

No one explains, anywhere, in any easy terms, how to actually install a turnkey "distro", which I've been told they aren't distros.

Installing should be pretty much self explanatory. It should be more-or-less the same as installing any other distro to bare metal. Download the ISO, "burn" the ISO to USB (or CD/DVD) and boot from it. Then follow the prompts - answer the questions where required, otherwise defaults should be reasonable, or tweaks stuff where you want.

Any specific problems, just ask.

Is there a visual explanation instead of a guy throwing technical terminology around as though I should know it?

Sorry I'm not quite clear what you would like explained visually? I get how visual representations of things can often be really useful, but TBH, I wouldn't know where to start to explain the whole TurnKey project visually?!

I'm more than happy to answer specific questions though, so if you have more, please ask.