MrSuper

Cat 5e is rated for 1 Gbps, up to 100 meters. Just an FYI. 
 
 
@MrSuper, technically PC 2 could pull up to a gigabit, but you have to remember that that internet connection is shared for all devices. Technically speaking the link between your main router and switch is 1 Gbps, its highly unlikely that one machines connected to the switch will pull the entire 1 Gbps at a time and saturate the connection. BUT if that were the case, you could saturate that Cat5e connection and have issues. Personally Id stick with what you have. If you end up saturating that connection the next step up is 10 Gbps gear and that can be hella expensive. A 10 Gig NIC cost are min $100, not to mention the Switches and Cat 6a wiring.  

With Cat5e, no.
If your switch is gigabit switch and you got load on the network from a server and access point you cannot pull the whole gigabit from pc2 as the maximume transfer is 1gigabit.
However the maximume will be 1 gigabit accross the network that is connected to the switch.

But that's just it, if you are running ethernet next to power cabling then the chance of it passing near switching PSUs or other appliances is fairly high.  AFAIK this is why its recommended to use STP for fixed wiring, but STP is useless in almost all home scenarios as your average router or switch isn't grounded.  STP wouldn't exist if there was no chance of EFI.
 
Plus I think we covered the "not likely to be a problem" quite extensively so not sure why you are accusing us of not knowing what we are talking about, you literally said the same thing but in far more words.

The ethernet cable is a twisted pair cable.
The twist in this cable is to make ik more resistive te EMI ( electro magnetic interference) which you power cable can make.
 
so there is no problem at al.

Its not recommended, but generally won't cause any issues unless you are trying to run a cable close to the maximum length of 100m.

shouldn't be that much of a problem

That makes sense, as only live will go through the breaker with the rest commoned, unless you are on an RCD/GFI or a different phase.

Not necessarily the same circuit, but they don't like to be separated at the meter level for sure, also they don't like surge protectors 

Typically needs to be the same circuit, seems likely both sides are on different breakers?  If so, not a good case for powerline.

I've tried that. And now I have also completely wiped my drives and reinstalled Windows and everything else. The problem is still here. 

It depends on the motherboard for the most part. If you just install a server OS that's designed to be controlled remotely, not having a GPU isn't an issue. However, whether the system will even POST without a display output depends on if the board supports booting headless. 
 
Bear in mind that if it doesn't, then it will require a GPU and typically something to output to as well. I run a FreeNAS server which boots into the OS fine without me doing anything other than turning it on, but the board won't boot headless so I need a monitor to boot. You can get dummy monitors though, which basically trick the GPU into thinking there's a display there, allowing a system to boot while basically being headless. So worst case scenario, you just need to buy a super cheap GPU and a dummy monitor/headless adaptor to make the system think there's a monitor connected and it should boot. 

jup, it usually is all or nothing. some boards might have a dedicated "charge port" or make one of the front usb act as a charge port but i have rarely seen that out in the wild if ever.
 
a different way to do this would be to grab 5V from one of the power supply molex connectors. those turn on and off along with the system.
 
there are adapters for this you can buy - search for "molex to usb power adapter" 

 
another benefit of doing it this way is that you can keep the led strips usb cable inside the case and hide it just like all the other internal cables 

Hm, no disk activity to speak of, no extra memory burden, no overheating, no nothing, just a dip in performance. Very odd... One thing you could try is turning off AMD Cool'n'Quiet in your BIOS, or going to Power Options->Change plan settings->Change advanced power settings->Processor power management, and setting minimum processor state to 100% to disable the CPU clock-down.
 
From there, my suggestion would be to run LatencyMon to see if it can capture some data and see if something's causing hard pagefaults or some kind of DPC issue while the game is running. If you export the view and attach/upload it somewhere we can read it, it might be possible for us to determine what's going on. I'd also recommend checking the System log in Event Viewer around the time the lag spikes happen to see if there's any weirdness going on there, as well.

I did it!! It was an program to make bigger text that was making this problem, i disablet it!