g el

Sorry those were keywords to get you googling
The graphical environment on a Linux system is not related to what distribution you chose. You can have your choice of a variety of desktops for any distribution you choose. The most common graphical environments you will encounter are GNOME which you will find on Fedora, OpenSuse, and recently Ubuntu by default. KDE is another big name, you will usually find it by default on Kubuntu and OpenSuse (they give you the choice when downloading/installing). Most of the graphical environment these days will have no problem working with touch screens.
Now when it comes to mint, it is refreshing yes. The Linux distribution mint, that was recommended in your thread several times comes with the graphical environment called Cinnamon... I cannot tell you more about that
Regarding SSH, you are talking about a server installation, you want to run a media server, that means you will set-up your OS, and Plex and then leave the system alone. That means that your choice of graphical environment will not matter. SSH stands for Secure SHell and is a way to access your system remotely to maintain it. On a server that makes much more sense then attaching a screen. If you want a server setup, you should be ready to learn how to deal with the terminal, you will not find a UI to configure every aspect of the system on Linux.

The issue as you describe it seems to be related to bootloaders. If you are planning to unplug an SSD and plug in another then you need a bootloader installed on both, or you need to setup Linux with the Systemd bootloader and just load it using the F8 menu (That will also be an option if you install a normal bootloader)
If you are planning to keep the windows SSD plugged in. You can also use F8 to switch, just don't install anything into the EFI partition on your windows disk. You can also, of course, add an option for your Linux system directly in window's EFI partition and rely on the Windows bootloader to figure it out.
 
Just to give you a short intro to booting on EFI systems. You usually have a small (500MB) partition that is formatted in FAT32 called the EFI partition. This is where BIOS will look in to boot your system. In there you will usually find your windows bootloader. If you install Linux on the same SDD or you use this specific EFI partition to set up the bootloader then you will also get the GRUB installation in there along with the Linux kernel images required to load the system.
By unplugging your SSD completely while installing Ubuntu, it will create your EFI partition for you on the second drive. This should ensure that your UEFI will be able to find it as soon as the disk is plugged. When both disks are plugged, the first in the boot order will win, or you choose what you want from the Boot menu (usually F8)
 
Regarding installing from windows, it is theoretically possible as installing Linux is just a matter of extracting your files in the correct directories (It is for Ubuntu anyway) and adding your users which could be done through a chroot so I guess the new Linux subsystem on windows can do that. But it is just hard to do, you have to get drivers for your filesystem types and learn about chroot and what it takes to configure a system, it would be much easier to and simpler to boot a USB drive and do it.
 
To get more understanding of how to configure your bootloader or system in general, I would recommend reading some of these articles on the Arch wiki. It is Arch oriented but it usually includes enough of the basics to teach you about a certain topic regardless of the system you have. Also, consider joining the Ubuntu forum they are (or were when I was active there) very helpful. Another source of information is the ##linux and #ubuntu channels on Freenode on IRC if you would like to try that old technology  
 

Since this is the non-windows forum, I would say come to the dark side, we have cookies
But seriously, go with 64bit

Since this is the non-windows forum, I would say come to the dark side, we have cookies
But seriously, go with 64bit

With arch you usually have a networking section in the manual where you learn about netctl somehow i always forget it though but just go to the handbook and look up setting up networking 
i believe it might be enough to do something like netctl enable and your network card and then maybe enable networking using systemctl 
anyway this what you should google for that.
if you plan on running gnome or kde though you might want network manager instead of netctl in which case you can skip this all together and just install the de from a live cd you can boot the arch installer again and mount what you need as if installing without formatting anything then you will get into your installed system then get whatever desktop you need and enable network manager with systemctl enable networkmanager and reboot
maybe also do systemctl enable gdm or sddm while there to boot to ui right away 

I have a oneplus 5 i like it. the jelly effect never bothered me while reading 
i like the buttons or i got used to them but i wouldn’t have minded more screen estate instead my previous phone was a nexus 5s and the fingerprint reader on the back was very natural.
i recently just got upsets with all the spying news with oneplus and i’m still waiting for oreo other than that the phone is good. Still maybe wait for the T to know your options 

Thanks for your reply, I might eventually add an HDD if I find my  space running out, or simply start adding some SSDs. I found over the past year that I have no more use cases for HDDs in a PC I switched the HDDs on my laptops with SSDs and got enclosures for them but never actually plugged them in. But for the use case of this new PC it might make sense. Or I might end up building a NAS

Hey,
could you post a bigger screen shot or a copy of the terminal output?
Also helpful would be your distro information
Is this a local server, or is it hosted online?
The output of systemctl status <service> might also be helpful here
How are you trying to install the software? Did you consider containers for this  (Docker)?

Hey,
could you post a bigger screen shot or a copy of the terminal output?
Also helpful would be your distro information
Is this a local server, or is it hosted online?
The output of systemctl status <service> might also be helpful here
How are you trying to install the software? Did you consider containers for this  (Docker)?

Hey,
could you post a bigger screen shot or a copy of the terminal output?
Also helpful would be your distro information
Is this a local server, or is it hosted online?
The output of systemctl status <service> might also be helpful here
How are you trying to install the software? Did you consider containers for this  (Docker)?

Arch can be as stable as you want it to be. That said it takes a lot of discipline not to use the breaking edge stuff in a rolling release model. 
 
My 2¢ 
If you felt more comfortable with one of the distros don't go hunting for more. As you get used to Linux you will realise that switching distros is relatively easy, as long as you keep your home partition separate you will not be loosing any data or even configuration, at that point the only advantage of one distro over the other is the package manager and the update frequency/philosophy

I did this really quick, and I'm sure others could recommend better builds, basically since you don't have load on the system you can go as cheap as you want.
I would still recommend Linux, if it's a storage PC your mom won't be accessing it directly, instead she will be only accessing a network folder from her own PC or any other device. Windows 7 here in my opinion is a waste of resources and money.
 
PCPartPicker part list / Price breakdown by merchant / Benchmarks
CPU:  Intel Celeron G1610 2.6GHz Dual-Core Processor  (€35.89 @ Amazon Deutschland)
Motherboard:  ASRock H61M-GS Micro ATX LGA1155 Motherboard  (€37.36 @ Amazon Deutschland)
Memory:  Patriot Signature 4GB (1 x 4GB) DDR3-1333 Memory  (€30.99 @ Pixmania DE)
Storage:  Western Digital Caviar Green 3TB 3.5" 5400RPM Internal Hard Drive  (€100.99 @ Pixmania DE)
Power Supply:  Be Quiet 300W 80+ Certified ATX Power Supply  (€46.93 @ Amazon Deutschland)
Total: €252.16
(Prices include shipping, taxes, and discounts when available.)
(Generated by PCPartPicker 2014-01-08 18:09 CET+0100)

Will you be using it only for storage or will you be connecting it as a media center or so? There's no room for more than 1 HDD so i'm guessing no RAID setups. I would recommend a low end board/cpu combination with focus on a big HDD. You could install linux on it and run it as NAS or so or use XBMC if you're looking for a media center setup