What's the difference? 😉
To be seriously now, if conf files with keyboardlayout=gr, value dependend of the language set to, placed in xxx.lproj inside the DOSBox app package,
DOSBox should read that config file by default (Mac porter attention here 😉 ),
but why not just add your keyboardlayout to your standard config file and lead DOSBox to that file in the first place (or last place, to force this layout), followed by further config files, if needed.
If you place a config file called "DOSBox Preferences" in your Preferences folder, it will be read by default all the times DOSBox starts, then followed by other config files you may add to the Terminal command line parameter.
Editing the "DOSBox Preferences" standard config file with the keyboardlayout setting seems the simplest way to me.
Is a localication to other languages than english useful to the DOSBox application? I think, it's not worth.
The language files available from the DOSBox site works well with the Mac port, so the DOS inside is localized at least.
To include a lang file in the Mac port of DOSBox, call DOSBox by using the Terminal (drag "DOSBox.app/Contents/MacOS/DOSBox") into the Terminal, add the parameters as usual,
for example -lang PathToLanguageFile -conf Path to ConfigFile.
An easier way to do so is to add " -lang " (w/o quotes) to the Terminal command line, then drag the desired file into the Terminal.