WoW Fullscreen stuttering, need some help

I try to keep this short. I always write like a novel when I’m mad.

I need some seriously help with my game and this Fullscreen(windowed) thing.
It’s constantly “stuttering”(very small fps loss, like 10-15) when I move camera with mouse or comes into fight. Very random it also freeze for a good 1-2 seconds. I have been going through so much stuff. Reinstalled,

Removed addons and all those WTF / Cache folders etc to no avail.

However, I fixed my problem now. I randomly switched my settings and took normal window mode and made it to fit screen. Looks ugly as hell to see a window bar at the bottom but the game is running so smooth.

Now for the help I need. What can I do to fix this?

I googled around and read some old thread but all ppl I see talking about the problem and this new force setting to dx12 and they also run minimum 2 monitors or even 3.

I use one… Old style for an old dude. I’m very extremely noobish now days how to update / fix setting etc in this game and or win 10.

Some help is appreciated from anyone that fixed or know the problem.

Regards

-edit- I forgot to mention that this problem is with Retail which I came back to after some years…(4 or so) this happened also in Classic but much less.(I dont play Classic much more now)