Ok, update.
I have been playing now in a Window (not borderless fullscreen) and doing some Alt+Tab back and forth into the game (also pressing "e" and "esc" but just 1-2 times) While sometimes i had to wait between 1-5 mins (!!) for the game to respond, i have been able to continue playing without having to kill the process, watching all cutscenes and cinematics.
I also have changed the compression of textures Off (i think for AMD are recommended to be ON but...i have nvidia so i tried) and cache textures to 32 pages instead of default 16. I have disabled V-Sync in the game and forced it with triple-buffering on the Nvidia control panel.
While some loading times are still very high, at least i'm able to play the game without having to quit and run again. I have experimented some stuttering in 1 longer cinematic but that's all.
Some things i have noticed:
-Recovering from death needs more loading time than restarting the game IF there's no cinematic or cutscene. I mean, if game starts directly into the action, then it loads very quick.
-Going back to the main menu from the game takes much, much longer than quitting to desktop, running the game again and resuming...lol (again, because starts directly into the action, i suppose)
-After disabling the compression in textures and making the texture cache double size, game is using just 2 more GBs in the cache pagefile (from 8 to 10 gbs file size) I have system cache disabled by default so system only uses what the game needs. I have the cache on my SSD, ofc, but starting my PC fresh without the cache already written in the disk makes little difference, game runs and loads to menu in a matter of seconds in both cases (i have cinematic intros disabled for saving time: +com_skipIntroVideo 1 as running parameter on Galaxy)
-After all, and as the game runs perfect while in-game, it may seem that this kind of problems come from loading the .bik and then mixing the sound in (from english.streamed, for instance) I mean, apart from the memory/cache issues the port has. I will have to download the steam version and see the differences here, maybe the bink decoder library is not the same version as in 2018 (i doubt it but will test)
I have a Gforce 980 with 4GB VRAM and 16GB RAM on system and except Shadows on medium, the rest of graphic options are HIGH or enabled. Playing at 1920x1080, but i have also tried 2K and game runs perfect except for the freezes when loading that are the same in both resolutions, no matter if lower or higher graphic options, etc.
As the GOG version must be (i suppose, except for the drm removal) the same i have already played before, the only thing i can think has changed is the graphic drivers. It's stupid but i'm thinking in downgrading the drivers until the minimum recommended by Bethesda/MachineGames (355 i think, have to confirm) and keep testing the differences because it's annoying being able to play the game before and now having all this problems.
In any case, the game's optimization is awful and all this problems are not new and i saw loading freezing reports since 2019 until now on Steam forums, maybe even more than before, not sure. No one has a single solution unfortunately, and it seems that crashes loading the game (a lot also in the forums) are related to this loading videos thing, at least for a good part of those affected (some were able to avoid the initial crashing skipping the intro videos, but again this is not universal)