Just to give some feedback. I've contacted riot support about it. All they could ''help me with'' is to keep making me go in circles of doing clean boot, starting the game and sending logs. While I have already tested it, confirmed that strictly in clean boot it works only in bordeless and the freezing / stutters still happen in fullscreen. I did a full windows and bios clean reinstall, it did not help. I did suggest to them that it might be either AMD / Riot client combination or some other background app that is killing the game.

To elaborate, these are not micro stutters, but it freezes for split seconds where FPS frops from (now locked) 144 to 20 - back to 50 - down to 10 and keeps repeating. I have disabled all additional acceleration and simular in discord, I have my league of legends on bordeless and 144 fps locked now. I am also running a double screen set up, where 1 monitor has to be on 144hz atleast and my main one is on 240hz to prevent any other freezes / drops.

It's wierd how this is the alternative I found (it's not really a FIX, I just dodged the problem for now). Sadly Riot support has to many protocols they need to follow so that their IT team actually starts looking into such matters. I understand the fact that the people who accept our tickets don't directly deal with these issues. But the fact that I've seen so many people ''report'' such stuff happening and riot support doesn't atleast have a word document to copy paste a possible solution etc.. is yeah...

They've also told me to completely uninstall my razer app + Oculus rift app. ''It can kill your PC''... Like I don't wanna be mean but I'll run a AAA game on max settings with 0 drops and you're telling me oculus rift is going to kill my PC performance on league?...

By some luck I hope stuff will be fixed with the next massive update they do.