I disagree about the darker honey. Best stuff I ever had was MD wildflower, a dark amber color. AWESOME stuff. Also Buckwheat honey is almost black and it is a very strong honey so it can stand up to almost anything you throw at it. If you want delicate flavors go with lighter honey. All depends on what you want as your final mead. Same principle applies to dark grains. If you want a stout you best use roasted barley.
Regarding head space, for primary leave some room for the active fermentation as there is some foam generated from mead fermentation. Use a bucket, carboy what ever, just leave some room.
I secondary, after your fermentation has finished, fill it up to the base of the carboy neck. Use glass for long term aging as O2 is NOT good for mead after fermentation is complete.
Use nutrients, if you have them otherwise go with about a pound of pureed raisins, the yeast love them!
Cheers!