PC Super slow after playing games?

DO NOT TL;DR !!!! I took the time to write this, then please take the time to go through it STEP BY STEP

lets do some basics to make sure 'under the hood' is as we expected first turn off ALL OCing.

Did you install all Windows Updates? Including OPTIONAL except BING? Check them and repeat till ALL are installed.

Download and run Slim Drivers, install all the latest updates but you don't need to reboot until you do the last update

Go to www.filehippo.com, download Malwarebytes, go to CUSTOM Scan and set it to do a full system scan (by DEFAULT IT DOESN"T DO THAT, and AntiVirus doesn't pick up alot of malware) - this resolved almost ALL other similiar posts to date as most had Malware the AV didn't pick up.

Remove whatever AV your using and download AVIRA, AVG, Comodo or Panda go to CUSTOM Scan and set it to do a full system scan (by DEFAULT IT DOESN"T DO THAT) - this repeatedly has resolved alot of people issue relying on MS Essentials.

Repeat the AV/Malware scans till the system comes up clean.

Download and run SPECCY, copy and paste the first tab to show your idle temps

Download AUTORUNS and turn off anything NOT critical on startup, so you don't need to run JAVAScheduler to check for Java updates everytime you start your computer for example. BE CAREFUL AND KNOW WHAT YOUR TURNING OFF BEFORE YOU DO IT.

Download and run MSI Afterburner, in the settings turn ON OSD, then go through and SET the stuff to 'watch' by enabling them in OSD (On Screen Display)
Now run some of the games that run poor, what temps are you getting when underload as compared to what you posted?
With MSI Afterburner Do you see anything funny that the CPU or other parts are maxing out (we are testing here not trying to WIN at the games, so if your screen is filled with readouts then just deal as we are just observing).
Do you see this problem when in SOLO MODE? Only when Multiplayer?
Check all the games you listed, and provide if there they ALL or just SOME are having this issue?

Open Computer, Can Air dust out the bunnies and use paint brush on the vents, coolers, fans, etc.

Go through and provide a response on each point, don't SKIP IT because "I ALREADY DID IT" , just try doing it again as of THIS post so we know NOW what is happening as compared to BEFORE you posted.

Yeah I would tell you untill you got proper cooling installed ALL YOUR PARTS are affected (it isn't just the GPU because that heat is inside the PC where ALL the parts including the HDD is). If you been 'putting this off' then you are / HAVE ALREADY DAMAGED Hardware and you will be looking to such results / inconsistencies TILL YOU REPLACE THE BROKEN HARDWARE.

TWO Key rules of PCs; NEVER mess with the Power (PSU) nor play with HEAT. Both kill / damage hardware too easily.
Considering the condition of your PC it does NOT look like it has really be maintained (those steps should be your AT LEAST monthly mantra) and most likely I would NEXT start (after getting proper cooling) with downloading DBAN and wiping then reinstalling Windows. If I see things act 'weird' when I try to DBAN wipe it, then I know the HDD is failing (as mentioned).

Please do NOT forget to select the solution.

Yeah Actually for a Sapphire R9 290 Tri-x that is actually damaging (causing the GPU core to microcrack as well as the VRAM) the components, depending on how long you been doing this (more then a couple weeks) will inevitably determine how much damage. Just like if you were running your car without enough coolant 'just to get back and forth to work' you still crack the Engine case and warp the pistons / rods that will cause the entire engine needing to be replaced. Just warning you up front.

And that doesn't count for the added heat being applied to the HDD because the Sapphire R9 290 Tri-x is spewing out it's "80C" into the case driving up that, the CPU, the RAM, etc. temps as well. Just saying, your literally melting down your parts internally.