Predator G6-710 - At wit's end with stuttering

Unconquered
Unconquered Member Posts: 23 Troubleshooter
edited February 15 in 2020 Archives
To preface, I'm not extremely well versed in computers, but I've picked up a few things along the way.

So, I've had this computer about four years, although I've replaced a few parts as time has went on.
Specs are the following:
Windows 10 Home
i7-6700k
GTX1070 (Came with 970)
16GB DDR4
128GB SSD (OS dedicated)
1TB Seagate Barracuda HDD
Corsair RM850W Gold PSU (came with a generic 750)
MOBO is Z170 (I believe, would have to open case to get exact model number)
---Firmware Version R01-A2

This stuttering has been happening for the better part of two years... or at least that's when I first noticed it.   It happens in games, it happens while browsing, it happens when opening the start menu occasionally.  Sometimes the stuttering is frequent and slight, sometimes I get .5-1s hangups.   Worst of all, I've been trying to stream to twitch using OBS recently, and it's just a disaster, huge frame drops which last up to a minute (though not listed in OBS log files at all), and after gathering advice and showing logs to people who are quite good at troubleshooting OBS, they are at a loss.  These stutters happen even in the preview, though not in game, and appear when trying to encode with CPU or GPU.  I'm not expecting anyone here to know how to fix that, but I want to illustrate how much difficulty I'm having pinning down this issue.

These stutters also appear noticeably in Heaven, and though less noticeably, in furmark.

Here's what I've looked into so far:
I've ran Memtest86 multiple times, last time was yesterday, 4 times at 4 passes each, with no errors returned
I've run the Intel Processor Diagnostics Test and passed
I've tested my VRAM in OCCT at 100+ iterations with no errors found
Check my SDD/HDD health frequently with CrystalDiskInfo, no issues
Set Windows and Nvidia to High Performance
Replaced the stock PSU, which was experiencing the same issues
Full reinstall of Windows twice
Nvidia driver reinstall, using DDU in safe mode first
Monitored HWInfo and observed no bottleneck in CPU/GPU at time of stuttering
Double checked both monitors set to same refresh rate
Haven't noticed anything in event viewer, though not sure exactly what to look for

I'm at a complete and total loss on what to do here.  I'm hesitant to update firmware, as I've never done it before and don't want to brick my PC; I'm not even sure that would help the situation either.

If anyone has any advice or ideas, I would be very grateful.  Thank you.