Regarding the first game UFO Enemy Unknown (which here is called X-Com for some reason, I remember there were two specific bugs which I was wondering if they have been fixed in the GOG release.
The difficulty setting resetting to easy on its own, and an item limit in terms of how many you can have. I don't remember the details of it, like the limit, the location applicable, etc, only that it existed.

I am talking about the release here on GOG, not using external mods.

Also, anyone knows if either of those bugs exist/ed in TFTD because I don't remember?

TFTD also come with xcom2_win_patched.exe or something like that - most updated Win version. Just like Steam. But GOG not point it include windows version, and link lead to GOG DosBox Launcher. Exe\link should be started\created manually. X-com 1 dont have windows version here. And so - not latest fixes. Latest fixes been made ffor Windows only Collectors\Gold edtions.
(also there is un-offcial fixes for WinVista support and those _patched.exe's from 2K is based on un-official community fixes).

Steam provide dos+win for both first games and ask which one to laucnh.

There is fixes for DOS version. Difficulty been fixed in old dos-time. Or exactly this is never fixed (as PCGW say, it been fixed in Gold). Some deffintly still there.

[url=http://www.pcgamingwiki.com/wiki/Series:X-COM]http://www.pcgamingwiki.com/wiki/Series:X-COM[/url]

UPD: GOG initially wrongly labeled Xcom1 as 1.4. Now is stated as 1.2 - 1.4 is more fxed Windows only version. DOS is 1.2 officially.

Be careful with DosBox settings recommendations there. As always (eg Quake 4 tweaks in config file) - too much options string posted by someone who have no idea what they do.
Read conf file explanation from DosBox carefully and edit t manually. First of for DOS veersion in DosBox - cycles should be auto with manually lower cyless steps and manyally change them by hotkeys - differ one for Earth mode and for battles mode (affect speed of globus timer increasing or decreasing battle speed or vice versa - if play on auto\fixed value and not change it by hotkeys during gameplay).

For OpenXcom. As always, those projects is not fixing-mods - it is separate products. Differ from sctrach AI. And it not 100% compatible with Xcom2 features. It enlarge battle maps from original XC1 game, but it still less than be in original XC2 game. Something that been changed from XC1 to XC2 like size not implemented. it based on one engine based n XC1.

As always - worth to try. Always - never to replace.

X-COM: UFO Defense has a limit of not more than 80 items on a transport, which in turn means not more than 80 items available to your soldiers at the start of the mission. You can partially mitigate this by scavenging equipment that the aliens bring to the mission. See also UFOpaedia below, or switch to OpenXCom, which does not have such a strict limit.

https://www.ufopaedia.org/index.php/Managing_the_Item_Limit

OpenXCom provide some fixes separate of their installer as data patch
http://openxcom.org/downloads-extras

OpenXcom is FAR from being accurate to the original game.



If you want to fix stuff just use "xcomutil" to fix the difficulty bug: https://www.bladefirelight.com/xcomutil/xcomutil-downlaod/


The difficulty bug only affects UFO and not TFTD.

Though xcomutil also has a few fixes for TFTD, for example the Very Small USO and the Small USO are swapped.