High CPU and GPU

A good 20-30 minute run of Prime95 is all you'll need. Run the blend test, as small fft is mainly for thermal testing, and you need that ram usage of the large fft test. You can also try running the built in windows memory tester thing for RAM to see if you've got dying RAM sticks. I kinda doubt it though.

I'm curious if you aren't maxing out system memory (RAM) usage. It says you've got 8GB installed, but it's only got 5.41 available. Check to see how much RAM you have listed as "hardware reserved". If you've got over 100-150mb in there, something's not quite right.

Try killing all background processes and see if that doesn't help. Uninstall stuff you don't need. If your CPU is hitting 80% just watching youtube and it isn't 10 years old and you aren't streaming 8k video (I torture my older computers sometimes for giggles, don't judge), I'd look at background processes as the main source of the problem. Do you have autodownloaders/installers running in the background? Anti-virus/security systems? Is malware running rampant? Your GPU usage looks fairly normal, and your CPU usage seems to spike with GPU usage, indicating that at least your system isn't mistimed.

Edit: It's called the Windows Memory Diagnostic Tool, at least on Windows 8 and newer.

Synapse doesn't play well with a lot of games. In fact, it's been known to trigger several widespread anti-cheat programs.

Running multiple security programs at once, especially on top of Window's own security system, is a really, really horrible idea. They're all attempting to filter each other's traffic, which leads to a needlessly costly feedback loop that eats all your CPU and RAM usage over time. Given that Overwatch is an online game, all your programs are constantly fighting for resources and run time to do all their filtering, leaving your game in the dust to run off of what's left. Try disabling them all through resource monitor/task manager (you can't get a virus while playing a client-based game, which has its own anti-cheat and security programs running; how else would they filter profanity?), or even uninstalling them, and see if performance doesn't increase.

Watch Linus explain why.

I looked back through the rest of this thread, scrutinizing it for details.

In your initial post, you said you maxed out your CPU temps? That's not good. In fact, that's horribad. Can you confirm?

80% CPU usage while fullscreening youtube?? Are you purposefully benchmarking 8k/60fps streaming? Otherwise, that's not normal. When I'm running youtube fullscreen at 1080p60, I'm using on average 15-20% of my CPU, and 4k will push that up to about 47-50%. 8k just murders my system, and pins me at 100%. It's strange though, since you say above that your idle CPU usage hovers around 1%, and Youtube browsing pushes you to 20%, which is very normal. So is it 20% or 80%?

Your GPU temps look good, seeming to hover around 53-55C under full load. I wonder what your CPU temps are under load? From what it looks like on that afterburner graph, when you're going through menus, you're pinned at 100% usage on a very light load. You then hit 0% usage as the loading screen is essentially a still image. As you get in game, your load decreases steadily over time until you ragequit. I think something is throttling somewhere, and I think it's your CPU.

Between standby ram and free ram, is functionally the same thing. Free ram simply means that it's never been written over for the time your PC has been on, and standby means it was written at one point, but cleared and released as ram to be used later. I think your ram is perfectly fine.

I would like you to try a couple of things, and see if they don't help.
1.) In afterburner, take that power limit slider and max it to the right.
2.) Lower your screen render percentage (whatever it's called in overwatch) to an obscenely low number, so that it looks like garbage. Does your fps rise significantly?
3.) Crank shadow, particle, decal, and ambient occlusion to maximum, turning off any Nvidia-proprietary features like PhysX, while turning everything else to a minimum, leaving the screen render percentage maxed out. How does that fps change from what you used to play at?
4.) Do the exact opposite of 3.) while leaving physX off. How does that change the fps?
5.) optional: run prime95 torture test with small fft's for about 15 minutes. What are your CPU temps?

I'm trying to figure out if it's a CPU or GPU limitation, and whether or not it's a hardware or software issue. 1.) eliminates bios limitations. 2.) lowers load across the entire system. 3.) loads the CPU hard, and minimizes GPU load. 4.) does the opposite of 3.) Keep an eye on temps and utilizations during 2-4 of both your CPU and GPU.

There are two conclusions I can come to.

1.) Your CPU temps are too high. 100C is where a CPU will hit the absolute thermal limit, give up, and shut down. Your motherboard has done a damn fine job keeping you at 99C so you don't fry your CPU. As your temps go over the safe limit of 74C, your clock speeds will steadily drop, and as your CPU grinds to a halt and information traffic backs up, your frame rates jolt all over the place, and your audio gets crackly. That was a key piece, since audio decoding and playback is handled entirely by the CPU. Bad CPU performance will ruin audio codec performance.

Your GPU is barely being used at all (it's only using 40% of the available 110% power limit). The GPU relies entirely on the CPU to send it information so it can draw the frames to send to your monitor. If the GPU isn't receiving that information fast enough, it sits there and waits, resulting in hiccups in framerate.

Check your CPU cooler and make sure it's mounted properly. While you're at it, check to make sure it's got enough thermal paste in there. There's too much if it's oozing out the sides, and too little if you haven't covered at least 75% of that top surface. You should be no more than 20C above ambient while doing light tasks like watching Youtube at 1080p or less. Also, check your case airflow situation. Do you have at least 1 intake and 1 exhaust fan? Are they both spinning, and fast enough? Which case do you have? Do you need more case fans? (I think you might need a better CPU cooler and better case airflow if temps are still high after this.)

The images from your initial post are incredibly similar to the images from your most recent post. I highly suspect this first conclusion.

2.) You're not receiving enough power to you components, exacerbating the problem. Which motherboard and power supply do you have (make/model)? There are a different set of symptoms which would demonstrate this, but a PC not receiving enough power could potentially force itself to sit at a low power state all the time, not letting you make full use of how powerful the hardware is. I highly doubt this one though, since you'd be experiencing failures to boot and frequent random shutdowns, or even corrupted bioses. Like an idiot, I totally forgot to ask earlier, so this a highly unlikely, but still possible outcome, ontop of 1.)

Let us know what you find.

A picture of the full inside of your case would be nice. I'd like to see if your case is getting enough airflow.

That thermal paste looks kinda grimy, but that's probably just the compound. You've got a proper amount and a fairly even spread. You also got the lucky batch of stock CPU coolers that have the copper slug in the middle, another plus. When you stick the cooler back on, make sure the plungers are pulled all the way out so the outer barbed pins go all the way through, and make sure you twist and push the plunger until it properly clicks into place. It's really finicky, I know, and it may require some foul language.

Just give me the make/model of your power supply. I can look up the rest from there.

You have a blower style GPU, which also, coincidentally, is one of the best dust magnets in the house, besides a vacuum cleaner. I suggest carefully disassembling it and cleaning it out as thoroughly as possible, remembering to clean off the old thermal compound and reapplying some new stuff, and not losing any of the thermal pads inside. A quick youtube search can definitely help more than me attempting to explain it in words. I suck with words. A graphics card cooler packed with dust can't cool anything, and while your system is partly disassembled for troubleshooting, may as well give it a thorough clean while you're at it.