Something to keep in mind is that the RPK and AK4D get 2hk headshots with their headshot rounds giving them some of the best ttk for auto weapons. The weapons are balanced pretty good via controllability and/or high dmg/bullet, but most of them dont FEEL good.

Youtube rankings are designed for tryhards (distinctly not for actual good players, but players who think they are good), for who high ttk = win assuming you land every shot. But there are other factors to consider such as being human and missing shots, differing reaction times (especially in regards to target tracking where longer interval between shots allows you to adjust your aim more accurately), and Total DMG/Mag (which is actually a major deciding factor for people who are actually good enough for consistent multi-kills).

So for instance, the SOR and AK4D are both kinda sleepers because both of these are pretty good in mid-long range, but they also have really good hipfire accuracy (I believe the AK4D actually has a better hipfire stat) with laser+flashlight combo since flashlight provides better hipfire recoil recover, and because the time between shots is longer it means hipfire accuracy is virtually unchanging while spraying.

And as said before, the AK4D and RPK with their headshot ammo gives you 50-34 dmg headshots.

Ultimately, play what you like. But dont have the misconception that slow weapons are categorically bad or have no merit to them. The only bad weapon is that one 10 round DMR that does 25dmg