Question New PC build stutters

[SweetPhilosophy]

Hello guys!
I have built this brand new build and I have the following issue: pc stutters first time when I open a game (or any app that uses GPU, such as OBS, and is the worst stutter) after a reboot and then I have random stutters in games (they are less noticeable). I would describe them like the PC freezes for a fraction of a second and then everything returns to normal. Some games capture this in the fps counter (such as league of legends).
A video with the stutter happening after a reboot when opening a game:

View: https://youtu.be/WPmv2Ze4rUM

A league game captures with RTSS where you can see the fps drops and frametime spikes:

https://imgur.com/a/ySiFaH0

View: https://imgur.com/a/ySiFaH0

At this point I'm suspecting the RAM (because if you look at the RTSS graphs, when a fps drop occur the RAM Usage will have a spike of load and then will free the memory slower than what the spike took from the CPU and GPU), PSU (because when a spike occurs the FAN speeds drop) or MOBO (or even the case, no idea how to test for MOBO, but for case I'm planning to run the PC outside of case these days) and honestly I don't know how to rule them out or fix it entirely at the end. The reasons why I'm not suspecting the GPU is because I managed to try it out in another person's PC with similar specs as mine and for the CPU there seems to be no stuttering when running CPU benchmarks like cinebench or even prime95 (maybe I could be wrong I'm open to suggestions).
I will post below my specs and troubleshooting that I did so far. Looking forward talking to you guys!!

Computer Type: Desktop
GPU: GIGABYTE GeForce RTX 3080 GAMING OC 10GB GDDR6X 320-bit
CPU: AMD Ryzen 7 5800X 3.8GHz box, 8 cores, 16 threads
Motherboard: ASUS TUF GAMING B550-PLUS
BIOS Version: Version 1804 2021/02/09 (latest, I have updated it)
RAM: Corsair Vengeance LPX Black 32GB DDR4 3600MHz CL18 Dual Channel Kit (CMK32GX4M2D3600C18)
PSU: Corsair RM850 2019, 80+ Gold, 850W, Full Modular
Operating System & Version: Windows 10 Pro 19042.867
GPU Drivers: Nvidia Game Ready 461.72
Extra build info:
Storage: 1x 240GB SSD for OS, 1x 1TB M2 SSD only for games, 2x 2TB HDD for random storage
CPU Cooler: Noctua NH-D14
Peripherals:
Monitors: ASUS TUF LED VA curved, 1440p, 27", 165hz, Free-Sync, VG27WQ1B, connected via DisplayPort (Primary); ASUS LED, 1080p, 24", 144hz, VG248QE, connected via DisplayPort (Secondary, Portrait Flipped)
Keyboard: Logitech G PRO
Mouse: Logitech G502 LIGHTSPEED WIRELESS GAMING MOUSE
Headphones: HyperX Cloud Flight, stereo, USB, Wireless
Gamepads: Wireless MICROSOFT Xbox One x2, connected through xbox wireless adapter dongle - not connected all the time, only when playing some singleplayer games.
Troubleshooting:

1. Enabling and disabling DOCP profile
2. Using different RAM frequencies
3. Installing AMD chipset drivers (with and without on fresh windows install)
4. Reinstalling graphics driver. Using Nvidia clean install, using DDU (safe mode, not connected to the internet), installed them using NVSlimmer. Also installed it without Nvidia HD Audio
5. Reinstalling Windows - no internet connection, clean install, deleted everything from the drive, hit next on the unallocated space, disabled windows installing drivers, installed them manually
6. Windows' Balanced (recommended)/High Performance power plans
7. Trying to uninstall AMD SATA AHCI Controller (I didn't have it and still don't have it but I looked for it)
8. Changing Communications Port (COM1)'s Flow control to hardware and disabling using FIFO buffers
9. Disabling Paging file, manually setting it, letting it on automatically
10. Disabling superfetch/sysmon service
11. Disabled HPET in Windows both in Device Manager and using cmd commands
12. Installed monitors drivers
13. Changed mouse polling rate from 1000 to 500 and then othervalues
14. Disabling and enabling xbox bar, dvr, game mode, gpu scheduling, .exe's compatibility mode/run as admin/full screen optimizations/high DPI settings
15. Checked for driver conflicts (events in device manager looked good)
16. Checked for GPU IRQ/MSI settings
17. Disabled windows defender, firewall, control flow guard CFG, data execution prevention DEP, mandatory ASLR, bottom-up ASLR, high entropy ASLR, validate exception chains SEHOP, validate heap integrity
18. Using only 1 monitor, each of them once (I had the 144hz one on my old build and everything was good, all peripherals too)
19. Plugging monitors in different DP slots
20. Disabling and enabling DDC/CI option of the monitor
21. Disabling and enabling AURA
22. Enabling and disabling RESIZE BAR
23. Disabling and enabling C-states
24. Disabling and enabling Gear Down Mode
25. Disabling and enabling Power Down Mode
26. Setting CMD2T to different values (1T/2T fixed for some people)
27. Setting Power Supply Idle Control from Auto to Low Current Idle and Typical Current Idle
28. Undervolting CPU
29. Disabling and enabling PBO
30. Changing PCIe from Auto to Gen3 and Gen4
31. Resetting CMOS
32. Removing HDDs, m2 ssd (after which things improved but the stutter came back the next day without installing it back), fan controller, case usbs
33. Connecting PC to another socket in another room and even in another apartment
34. Connecting GPU to other PCIe slots in the PSU
35. Swapping RAM sticks in their slots (I'm using the correct slots DIMM_A2 and DIMM_B2 as per MOBO user manual instructions

    https://imgur.com/a/1v3aadx

    View: https://imgur.com/a/1v3aadx
    ). Tried with 1 stick at the time (In the DIMM_A2 slot as per user manual) and this cause loss of performance of around less 20 to 40 fps in Apex Legends
36. Ran LatencyMon which showed a high DPC execution time on nvlddmkm.sys, thing that made me contact Nvidia support:

Nvidia specific troubleshooting - I spent several days with customer support trying to fix, in the end they told me they would escalate to Level2 support, but before that I want to make sure this isn't related to something else:

1. Enabling and disabling FreeSync
2. Enabling and disabling V-Sync
3. Power Management Mode - Prefer Maximum Performance
4. Low latency mode off/on/ultra
5. Nvidia Debug mode
6. Threaded optimization on/off
7. Hard capping fps to below refresh rate
8. Disabling all non Microsoft services
9. PhysX settings Auto-Select (recommended)/GPU/CPU
10. Confirmed that GPU is connected via 2 separate cables to PSU
11. Changing GPU slot (which caused really poor performance because the other slot was PCIe 3) and moving it back

 

[logainofhades]

Did you enable XMP, for your ram? Asus I think calls it DOCP or something like that.

 

[SweetPhilosophy]

Yes, it behaves the same with both DOCP enabled or disabled as well as different frequencies for RAM. I also ran memtest86 for around 12 hours overnight and didn't get any error related to ram