I'm going to assume you're using official, paid-for GOG offline installers. Other installers will work the same way.

I have a directory for non-Steam games mounted at /games. Every game has its own directory, and a game and prefix directory for the game content and the wineprefix respectively. For example, for Cyberpunk 2077 you would run mkdir -p /games/cyberpunk-2077/{game,prefix} to create the directory tree all at once.

To install the game, I simply use wine to execute the installer with the prefix directory set as the wineprefix: WINEPREFIX=/games/cyberpunk-2077/prefix wine SETUP_FILE_NAME.exe. The root filesystem will be mounted as the Z: drive -- use Z:\games\cyberpunk-2077\game as the install path.

I use Lutris to launch the game. Add a new game, choose "Locally installed game", then set the executable path to the game's main executable, the working directory to the game directory (usually works, some games expect a different working directory), and the prefix to the prefix directory.