Ok so in a last ditch effort to try to resolve my problems before initiating a RMA process, I was poking around my case looking for anything I oversighted and one of my water cooling tube got loose and started leaking in my case (this is the kind of luck I've been having lately lol)... I ended up completely dismantling my pc to cleanup the mess it did, dry off everything overnight, and then redo the loop. After that little adventure, I then proceeded as follow:
-Flash BIOS to older version for the Crosshair Dark Hero (3601 vs 3801 which is the newest) and then manually set RAM speed and timings everything else on auto.
-Fresh windows install (No internet and therefore no Microsoft account linking)
-Manual update of Nvidia Drivers, AMD Chipsets and other drivers (Downloaded beforehand on a USB drive)
-Restart - Connect Wifi/ethernet - Windows Updates - Rinse repeat
-Manually Install Realtek Audio Drivers following this procedure (Thanks to MoKiChU BTW) :
https://rog.asus.com/forum/showthread.php?117596-DRIVERS-Realtek-Audio-(MB-Intel-2xx-3xx-4xx-5xx-amp...-Progressively re-install other drivers and softwares (Armoury Crate/Corsair iCue/etc)
So far, I've used my pc for 8-12h for the past 2 days and I don't want to jinx myself but I'm happy to say I haven't had any major hiccup or stuttering issue since then. I'll still have to test running my RAM at higher speed since it's not running at full capacity and also maybe try again on the cpu undervolting. In any case, if the issue comes back then I'll start a RMA process but so far so good!