lotusmar: Szwagiermc a request for a detailed description of how he could start a game for 2 computers on the home network or via the Internet I will add that the WAR.exe file does not start in win 10.
Since you are new to GOG I explain two things.
GOG support site have dedicated pages to every game, sometimes with useful information. Sometimes that info are missed (previously available). Sometimes useful info placed only on one page of the games series. Diablo have useful info about tech problems also with War 2, but War 2 to not have that troubleshoot.
Some general articles about Windows, Dos+DosBox/DosBoxEr (Mac), and ScummVM engine.
Warcraft 1 have 'start multiplayer' instruction on it own page. Same as DosBox Wiki and PCGamingWiki articles about DosBox multiplayer emulation.
GOG sell usually DOS versions for that old games. Even if original release is Win+DOS or Apple Mac + DOS. Warcraft 1 bundled with .cue image file that contain full Mac+DOS.
DOS games can be started on Wi dows NT only in DOSBOX. GOG already place each bat/links for single online or settings.
Some manually ini editing is recommend for dosbox conf file. But game must start "as is". It just about appearing and game speed (mac version have update with resolution/window mode missing fixed in GOG config tool, but on Win still no that options - manually edit dosbox.conf).
You cant start game directly by WAR.EXE file. For online play GOG Galaxy client have separate execute option in MORE section.
Sometimes better install fresh version DosBox from official site. And copy it to game folder with new conf file (again, manually edited). Not necessary for Warcraft 1.
Some games are bundled not with DosBox but ScummVM. It not emulator but separate game engine. Unfortunately that GOG releases do not provide original game exe for using with DosBox or another version of ScummVM.