I have installed the gog versions of the original Baldur's gate 1 and 2. Even installed the widescreen mod but it does not work. Tutu does not run in full screen. Please help.

The configuration does not depict resolutions beyond 1024 x768. I had set the widescreen mod to full hd but to no avail.

If I downscale the resolution to 1024 x 768 it shows black bars at the side, due it being a widescreen monitor.

Firstly, the widescreen wasn't designed for modern systems. While you can play Tutu at 1920 x 1080, it doesn't scale and your avatars, along with the writing would be tiny.
I would suggest 1280 x 720 as a good compromise.
Make sure you start a new game if you change the resolution with the Widescreen mod.
As to it not running full screen, firstly, did you actually get to Candlekeep. The character screens won't be in full screen.
Other than that, you might have to change the scaling options in your video card's display panel.
Switching your display scaling from display to GPU, or visa versa, or overriding the scaling options set by games. See pic for Nvidia options.

Appreciate the help. My laptop has AMD integrated graphics and Nvidia discrete graphics, which can make things somewhat convoluted. Nvidia control center was not helping and I realized that the display scaling was being taken care of by the integrated graphics instead. I re-installed my radeon catalyst drivers yesterday.

Now, the gpu scaling works on lower resolutions, and the black bars have disappeared after using catalyst. The game still does not run in fullscreen for some reason (tried toggling between windowed and fullscreen modes) and using alt + enter.

Even uninstalled the widescreen mod, tutu, and re-installed them again. I installed tutu first and then the widescreen patch.

Will ignore the menu and check if it is fine in-game like you say. Shall also force it to use integrated graphics and see if that works.

Thank you for sending this.

Tried this. Got a 'no cd error on disk 2' which is super strange as it was my first time entering the game on tutu. Edited the baldur's ini file in tutu but the problem persists. I was keen on playing the original games. Will give it a shot later and install everything from scratch.

These are the settings that I used:
HD0:=C:\GOG Games\Baldur's Gate Tutu\
CD1:=C:\GOG Games\Baldur's Gate 2\data\
CD2:=C:\GOG Games\Baldur's Gate Tutu\data\
CD3:=C:\GOG Games\Baldur's Gate 2\data\
CD4:=C:\GOG Games\Baldur's Gate 2\data\
CD5:=C:\GOG Games\Baldur's Gate 2\data\
CD6:=C:\GOG Games\Baldur's Gate 2\data\

For now, the games do work well from the gog client on lower resolutions. Nevertheless, appreciate the help. I also spelled Baldur's incorrectly in the title here.