The 'carte de legitimation' gives rights to reside in Switzerland without visa. When travelling to other EU countries - particularly France, (by train only) is it enough to carry only this carte?

No, by rules, card by itself is not enough. You should also carry a passport. However, it's easier near Geneva border posts. However, if you go far enough, I suggest you take your passport. Also, some airport workers in Spain aren't familiar with the carte - they kept insisting that I needed Schengen visa - only after they called border patrol - it got resolved.