Sir0Tek

What is your budget, what is your actual gpu, what ram are you using and where do you live?

Arch (Manjaro) also offers a great wiki, for Intel gpus you might find some useful information here: wiki.archlinux - The wiki also has information on how to tweak Firefox/Chrome, hardware-acceleration and countless others.

May I ask in which situations any of these distros do feel sluggish, and where/how exactly Windows does feel snappier? It may be due to a few settings. Distros are usually build to run on any system so some settings that could cause troubles are set to very tolerant values. Some of the additional features of your igp may still be unused due to missing packages which are irrelevant for just running the system but do give a boost in certain circumstances; for example vaapi, vulkan and so on. Since your using your igp you can check how much vram is given to it by the bios. It should be on auto usually.

Fattydove is probably just a rebadged standard-ssd made in China, maybe it's equal to Zheino.

+-275 buys this: I3 8100 and you have to add a good graphics card.

How old is your psu, give or take? I get the idea it is been in use for several years already, without the need to push a rx580 within its life, let alone the Nitro. Does the psu have the correct pcie-connectors to fit the Nitro? And the gtx 960 also fails while consuming less juice...

The G3258 single core at 5ghz will be about as fast as the Ryzen 3600 stock/turbo. Some 'regular' cpus out there aren't that fast, like the 3200g for example. Is it worth it? No. Worth breaking a sweat oc'ing an old cpu in order to get a performance beating the I3-9100F? No.

And this is simply not true.

Cheapest? Cheaper than fx4300? Or I5 2500K? Or a delidded i5 3570K? Yes, the first one still sucks, the 3570K is competitive. Or try one of these unlocked Pentium Gs, dual-cores that pair a good ipc with good oc-capabilities...

I had a netbook with some slow 60gb 1,8" zif-harddisk and I tried to replace it with something bigger and faster. I ended up buying a cheap 128gb msata ssd and additionaly an adapter zif2msata for less than $20 in total.

Due to this sudo-thingy it's probably Debian based, maybe an Ubuntu-derivative like Mint. Or are you more interested in the desktop-environment?

Ehh, 500mhz memory speed is normal for the Vega56, not to confuse with the ddr4-memory.

I am quite sure that you can save different bios-profiles and reload them if needed.

This does not look good. You'll need to replace the electrolytic cap at least, the one with the burn-mark should be a capacitor as well, a ceramic one, which may still be fine.

The market with 2nd hand computers and parts in the Netherlands is somewhat special. Lots of dealers try to make a living with old parts and computers, you have to find individuals trying to sell their rigs and you need a good knowledge about the parts. It is not difficult to get a bargain but quite often you have to communicate with the seller due to him having no idea about the actual value of his computer. For example, If a seller saw the latest price of his 120gb ssd at €85,- back in 2016 he'll try to sell it for €65... Your advantage: There are a lot less buyers than sellers, if someone doesn't want to sell at a good price just ditch it, next one.