Yeah, but it only happens in opera.
Opera is iirc Chrome-based browser, and chrome works perfectly fine (tho i can't use multiple tabs on it, eats RAM alive)

Discovered the issue, at least for youtube.
The subscriptions container thing is throttling.
The fix, some time ago would be changing site preference (#guide-subscriptions-container {display: none;}), but now as opera doesn't let me change that for some retarded reason, what to do?

Oh, sorry.

It's Opera 32.

So, for some time now, I'be been having a ton of performance issues.
For instance, some sites take several minutes to load, while I do the same on Chrome (tho Chrome is a tad too heavy for 4GB of RAM, especially with 5-6 tabs open) and it opens it quickly.
And even more recently, for instance -> on youtube, when I'm trying to post something, or look for a song on it, or just go through my favorites, it stutters like crazy. Letters pop in after several seconds, the scrolling is sluggish, and responds only after a few seconds.

The only things I've changed from the default is the ABP. Actually, it's disabled on most sites.
I've cleaned it several times - cache, cookies, history etc. and it remained slow.

I doubt it's hardware-wise. My PC isn't some uber gaming PC that costs 3$k, but it has:
-Athlon II x4 600e
-GTX 650
-4GB of RAM
-Several HDDs
Temps are good. Task manager shows nothing out of the ordinary - CPU usage stays around 25%, while RAM is ~75% (with some other stuff in the background). Hard drive isn't loaded at all. 2 SSDs (120/80GB) + 1TB WD Enterprise SE.