Needed Material:
1.DosBox xBRZ - sourceforge.net/projects/xbrz/files/DOSBox/
2.VirtualMIDISynth - coolsoft.altervista.org/en/virtualmidisynth
3.FatBoy Soundfont - fatboy.site
4.Dark Forces Dehacker - ctpax-cheater.losthost.org/htmldocs/trouble.htm#df

Procedure
Step 1: Download Dosbox with xBRZ scaler and extract all the files, except the conf file, into the dosbox folder inside the game directory, then remove the dosbox.exe and rename the dosbox xBRZ.exe to dosbox.exe.

Step 2:Download and install VirtualMIDISynth with the Soundfont (Check tutorial on youtube)

Step 3:Download DFDehacker and extract it to the game folder, then open DFORCEDH.exe with dosbox.

Step 4:Choose Hacks Setup on the menu and select the following options:
1.Always jumping while Jump held down
2.Mouse Fire Secondary instead of Strafe Mode
3.Increase Mouse Sensitivity by 4 times
4.Standard Vertical Mouse View

Step 5:Go back and choose Configuration Setup, configure the keyboard to your liking, then Configure Mouse must have the following settings:
Turn Left/Right X Axis
Forward/Backward Y Axis
Fire Left Button
Strafe Mode Right Button
Then Save Changes and exit

Step 6: Go to GOG Configurator and choose the following settings:
Output:OpenGLnb
Scaler:none
Uncheck Aspect Ratio and Double Buffering
Resolution: original

And that is it, enjoy!!!

Maybe you could explain why you believe that these settings are the best. I think especially using a scaler is very subjective. Personally, I haven't found any scaler that I like. I tried xBRZ, but I really can't stand the look, although I understand if you prefer that. It's nice to give an "all in one" guide on how to improve the game, especially for first-time players who don't even know it's possible. I'd just like to give an alternative opinion:

I prefer the raw unfiltered, pixelated look, which is why I set up DOSBox.conf like this: On my 1920x1080 screen this results in a very sharp, unfiltered image scaled by exactly 5 times from the original resolution (320x200). Using "OpenGLnb" (OpenGL with "no bilinear" filtering) makes for a much better performance than the standard DOSBox settings, I totally agree on that part.

Regarding MIDI soundfont, I haven't tried your settings, but found that using "General MIDI" for music makes a great different to the sub-par default settings. This can be set by starting IMUSE.EXE (drag the IMUSE.EXE onto DOSBox.exe), press "c", change "Music" to "General MIDI" and "Port" to "330 default", then exit and save the settings.

Lastly, I can't praise Dark Forces DeHacker enough for changing the controls, especially when new versions are released.

[edit]
Made a mistake, the game's resolution is actually 320x200, not 320x240. So that needs to be taken into account for the fullscreen resolution.
Also, maybe using "aspect=true" is more accurate to how the game is ment to look. That makes pixels uneven (In my example each original pixel will be scaled to 5x4 pixels, making it look taller. Here's an explanation of what it's like in Doom:
https://doom.fandom.com/wiki/Aspect_ratio

Thanks for your opinion!

I actually tried to get it somehow close to DarkXL, since the project was never finished.
I like the smoother textures in some parts, that's why i chose that scaler, but everyone has it's preferences and i respect that.
The dehacker was the only tool i found that provided proper mouselook, that's why i chose it.
Anyway, i'm not that much of a specialist, so i just did the best i could and i think it was a good effort.

Please explain in more detail how I open DFORCEDH.exe with DOSBox. I'm too stupid to figure this out. :D

Thanks. In the meantime I figured out another way by changing SETUP.exe to DFORCEDH.exe in the "dosbox_DF_settings.conf" file. Mouselook works great and it feels like it was always already there but never 100% activated. This should be bundled with the game by default imo.

I can't find the YouTube Tutorial for CoolSoft Virtual MidiSynth. Which soundfont should I use?

Edit: Nevermind. I got it. I got turned around. Sorry.

I just want to say thanks!
I just finished a for-old-times-sake replay with these customizations.