Does a higher resolution/aspect ratio affect a line of sight? I want to play the game widescreen since it is more natural for eyes but i dont want it to be a cheat giving me an advantage in discovering enemies quicker than in the original 4:3.

Widescreen mod increases the area that you can see, but not what your characters can. So, the fog of war will be the same. In the original BG1 the actual screen is smaller than what your characters can see, so you could treat it as an advantage when you use widescreen mod.

Personally, I don't use widescreen mod and just have black bars on the sides of the sceen, but my monitor is quite small (18,5").

Hi!
Glad to see that there's still some praise for vanilla BG experience. I too realized that EE isn't really THAT BG really, so I'm on my way to start a journey and I've stumbled upon some difficulties with resolution modification (the only mod i'm going to use really).

So the resolution mod works fine itself, but the UI mod wasn't finished AFAIU. The maximum resolution I can have with it's latest version is 1280x800 which is quite OK on my 1440x900 screen, but.. something making me think I'm missing something. So I'm thinking about ways I can adapt this limitations. Is there any possibility to play 1280x800 with like black frames (like in window)?

Please share some wisdom how you deal with this modern hardware nowadays. Thanks!

The way to have black bars/frames on the sides (or all around) is to enable the aspect ratio in your graphics card settings. For example I have AMD card and in the settings I can choose:
1) keep aspect ratio (this gives me black bars on the sides) - this is what I use
2) full screen (screen is streched to the full) - looks horrible, especially for the games that support only 4:3 resolution on 16:9 monitor
3) middle (this gives me black bars all around)

Can't thank you enough friend, works very well for me!

Would anyone advise how to make the experience better playing on a modern LCD?

I've downloaded the newest version of wide screen mod, and tested on the original GOG version of BG1. It does work. However, it just seems reduce the FPS and totally ruin the playability! The higher resolution, the more laggy the game. In other words, the best gameplay is only under the original resolution.
Tested on my Surface pro 1796.

Look for a program on steam callled "Lossless Scaling". It might be what you need.

Installed both widescreen mod and GUI mod but when I start BG1 I go to black screen and can't get out of it. I have to turn my computer off to release it. I've tried several times but no success. My laptop has dual video Intel/Nvdia GTX1060 and I've try setting to the Nvidia only.

Any idea how to fix?

If you want to play this how it was meant to look (i.e. not completely zoomed out so that everything looks like ants; no offense intended to the widescreen/HD mod), download the "Integer Scaling" application (completely free). Run that app, start BG installed from GOG without any mods, run the game in a window, and then press ALT+F11. The application will scale the game up to a 1280x960 borderless window in the center of your screen and it will look marvelous.

Thank you for this excellent thread. I've just installed all the mods (except for the widescreen, instead used the Integer Scaling application recommended above) and as it is my first CRPG I am truly looking forward to it!