Mysterious stutters in Pop!_OS fixed by resetting monitor refresh rate

I was experiencing a mysterious issue on my Pop!_OS installation … I was having random & frequent stutters, sometimes it got way more serious and caused system freezes. My device is a pretty high end business laptop so these shouldn't really had happened.

So I struggled so hard on Internet trying to figure out what is wrong with my hardware or system configuration.

I tried disabling swap, decreasing & increasing swappiness (It's an NVMe SSD, no worries) and setting CPU governor to performance. But none of them worked.

Later like two days ago I found an interesting comment on how monitor refresh rates affect video playback. At first I just ignored it: it was about video playback, not much a big issue compared to mine, they are totally different; and, how possibly could display refresh rates cause stutters on a system wide anyway?

But yesterday I suddenly remembered two things, I did change the refresh rate sometime ago, and I did have a good time enjoying this beautiful GNU/Linux distro without stutters. Figured out there must be some kind of connection in between, I decided to give it a try. And hell yeah! The stutters are gone after I set the refresh rate to 59.96 Hz, which should be the monitor's supported refresh rate.

I'm using Dell's XPS 15 9650 with a UltraSharp 4K Ultra HD Display. It is supposed to be a 60 Hz one, but the Pop!_OS actually gives me 4 options, including 2 around 120 Hz. Oh System76, why the heck is that?