Pumbaa

The stand itself could act as a simple switch for the orientation. You are right VGA connector does not have an interrupt pin. I didn't check the others. The graphics card detects loss of signal and reads out EDID information from the monitor. So all it needs is sending no frames for a splitsecond during the tilt.
 
honestly without minding the details I feel like technology is already there! Every monitor supports EDID and every graphics card detects loss of signal. Most OS reads out EDID and sets desktop environment based on monitor capabilities! So we have the OS, we have the driver and the hardware for it.
 
a guy made a DIY project using arduino, accelerometer and python. here is a nice demo video:
 
Notice the screen blackening out during reorientation. This does not happen on a tablet or smartphone. So it also depends a lot on your expectations. For me the blackening out would be totally acceptable!

If you say what motherboard you have (maker and model), I could point out what component could be the culprit. 
 
You can then try to gently press down with a finger on that component while you hear the buzzing to see if anything changes, and potentially put some insulator around the component (some heatshrink tube that you can heat up to shrink and squeeze that port), or some putty (soft non conductive material like gum to absorb the vibrations)

Well crap.  You'll want to focus under that vrm heatsink / shroud, you need to look in the area behind the usb connectors on the io shield. So to go any further, you would have to remove heatsink, check components, put the heatsink back... it's a pain in the ass. 
 
Sadly, can't find any picture on the webs with that heatsink removed to show the components between the io shield and the row of mosfets that are part of the vrm. 

No, it's not something going terribly wrong and it's probably not a capacitor but an inductor.  You have solid polymer capacitors on the motherboard, which don't have electrolyte or moving things which could vibrate and make buzzing noise. 
Inductors on the other hand are coils of insulated wire wrapped around a ferrite or other kind of magnetic core, and when current flows through that wire, the wire can vibrate/scratch the magnetic core and you hear that buzz. 
The current may increase when you press multiple keys because you have more leds lit up on the keyboard, or you're sending those keys repeatedly to the computer, who knows.. 
If you hear the noise in speakers or headphones, it could simply be electromagnetic radiation from the power supply feeding the usb ports being picked by the speakers/headphones cable / audio connectors.
 

Yeah you can create macro commands, some have extra keys on the side, I have one like it. Though you can program the keys to what you want. You can also have profiles, each having different set of macros. Not sure about Linux but I take it it should work. Some keyboards can be customized without software. Depends which ones and if there are limitations to it. 

They would need an accelerometer and some way to communicate that information to the computer. I do not know if HDMI/DP have this ability. DVI/VGA would not have this ability. Plus the OS would either need to know what to do with the information or have software installed that would tell it what it does. This would add complexity and more points of failure to a monitor. In theory its great and most likely it will be done in the future as we see it on the apple pro display and some very high end monitors for drawing and such. 
 
As for the price, there would most likely be a cost associated for new monitors having this feature. Since there would be people who have to design how it works and make sure it uses either the software designed for it or that OS knows what to do with the sensor information. The cost of the sensor itself isnt that much (most likely a few $ at most), the cost would be for designing and implementation.

as far as i know only the Apple Pro Display XDR has something like this (if i recall correctly a review of it on youtube mentioned it)

absolutely need to get more information from your friend.
 
Laptop model and specs
what do they define as "slow"
what is he doing when it stops responding?
plugged in, or on battery power?
before the program stops responding is there a load on the GPU?
 

HDDs have overhead required to lay out the sectors and other things the software need to use it.
Think of it as page numbers, chapter headings and indexes. A pack of "paper" is completely empty, but arrange it in a book, and some of the blank space on a page is taken up and used just to fit page numbers on it.
 
So that "in use" is bare min of what is required to run the drive in an operating system. If you blanked it out entirely, it would be "empty" but not useable.
[edit]
Ext4 also has a min file length of 255 bytes. Also "Most SSDs have blocks of 128 or 256 pages, which means that the size of a block can vary between 256 KB and 4 MB".

No, they aren't. I use lxc-containers all the time. You *can* restrict the number of cores they're allowed to use, if you want to, but by default there is no such a restriction.

If it doesn't matter if those jobs run a little longer, you could run them in an lxc-container and restrict the container's RAM-use to, say, 12GB at max, so there'd always be a few gigs left for your desktop-tasks. Could also run the lxc-container at nice-level of 19.

Is this what you need?
 
https://www.tp-link.com/latam/download/Archer-C2.html
 

Get your boards software. Bois normally shows it but in a monitoring tab. 
 
Hot to the touch isn’t a big deal. I’m sure if you have a decent card it’s hot to the touch under use too. 

Couldn*t find it on HWinfo. I was looking into the Bios, it sais M / B temperature 33 deg. celcius.
 
If that is the right parameter then everything is fine. I felt like it is a lot hotter but maybe I am imaginating things
 
 
thank you for your help

HWinfo's sensor mode should be able to read it.

It's unlikely you'll massively break something in Mint, but double checking important commands (especially ones involving sudo) is useful. Just keep the OS separate from your documents (and keep backups of important data) and don't run stuff like "sudo rm -rf /* --no-preserve-root"   (really, find out what stuff does before running random commands from the internet or guides).
Anyway, you don't need to install the same OS twice to be safe from failures. Create a separate root parition where the main kernel files etc. are and you're fine. Should you majorly screw up your installation, just reinstall this and you're good to go again. I usually format my Linuxes like this:
/boot   - self explanatory
/          - root partition, ~30GB or something depending on what stuff I'll need to install.
/home - your stuff,  whatever is left after the other partitions have been made.
swap  - swap space, if you want, ~8GB. I wouldn't waste too much space on this.

I agree with tikker.
 
You are trying to usea a wrong solution to a vague imaginary problem.
 
Most important data is the user files. You need to back up thesein any case, especially if you plan on sharing user documents between the installations.
 
Linux is not Windows; re-installing is actually rarely needed, but if it is, your user files, documents (and settings) are already in /home (which is usually, but doesn't need to be, on a separate partition). Just preserve /home when re-installing and your "stuff" is still there!
 
In addition to user documents, other stuff to back up to speed up recovery in case of failure (say, your hard disk), is to back up any modifications you might have made into /etc, and perhaps a list of installed software (so you can just give a single apt-get command to re-install everything instead of incrementally re-installing stuff once you remember what you are missing).
 
That being said, if you'd get your Linux installation into a nonbootable state, it will most likely be the bootloader being hosed up; in which case another installation will not help you at all, since there can (usually) be just one bootloader, and if it is hosed up, you can not boot either of your distributions / installations. So, you'd need something else to boot and fix the bootloader (a Live Linux USB stick will be handy). In case it is not the bootloader, but the installation is otherwise messed up, it can be equally well (if not more reliably, say, because of a near-failed HD) fixed from a live Linux image (USB stick) rather than a full-blown installation on the HD.
 
TL;DR: Double installation is absolultely unnecessary and redundant