Hello once again.
I have some updates. Some days ago W10 send me a notification saying I should restart in order to 'correct errors from the unit'. I did as the system said, and since that I did not have any issue regarding the instabilities. I can still find the 'GCUBridge stopped working' in the 'system error logs', but the laptop feels clean.
Since I'm no Windows expert myself I did more research about those black screens I once had, and apparently they are normal once you turned the pc/laptop on for the first time. I read something like this: "...Windows may restart the graphical server sometimes in order apply the driver's updates to the OS...". And honestly it feels like it was it.
I had two black screens when I first booted up the laptop with the new SSD, think about it, 2 GPUs, 2 black screens. I'm starting to believe that maybe the issues could be with the drivers after all. But if the issues were truly with drivers, what was I doing wrong? I tested all the drivers available...
Thinking about, maybe the issue was with the nvidia-prime? I did not try to run with optimus, in the Windows like mode after all...
Anyway, I'll give the laptop some extra W10 days just to make sure it is working like a breeze. In this weekend I'll contact the support and see what they think about it all.