Any problem Desktop games only with .ogg ?

If i remember well the .ogg and .m4a are generated due some browsers accept one or other format or something like that. I don't know if still exist the problem.

BTW, if the game is gonna be only fos desktop, is there any problem if only use the .ogg format to save space, organization,etc... ?

I don't think there is a problem with .ogg if the end goal is just to create a desktop version. But you want want to consider using .m4a if you ever want to be able to play it on a Xbox One, since it does not support .ogg or atleast a couple of months ago it didn't.

NW.js supports .ogg so it's the only audio files you need for that platform, but C2 should automatically remove other files when exporting to that platform so there's no need to remove files yourself.