how much yeast?

I've been making mead recipes from a book. Each recipe is for one gallon. Each recipe recommends one package of yeast. If I want to make 2 or 3 or 5 gallons, should I increase the yeast amount concomitantly? When I make regular wine, I still use only one packet. Would more yeast produce more alcohol, or would there just be too little food for extra yeast? What yeast is best for mead: montrachet, champagne, or are others (I prefer dried packages rather than liquids)?

The Great Mead Experiment is on this page. They compared five or six different yeasts.

Two 5 gram packs of dry yeast should be sufficient for a 5 gallon mead. Don't forget to proof! One pack should be enough for a 2 or 3 gallon batch. More will not hurt, but might be a waste though it's doubtful a homebrewer could overpitch.

More yeast will not make more alcohol, only more sugar ( a higher OG) will.

The best mead yeast? That's entirely up to the meadmaker...

One packet of yeast is good for up to 5 gallons, extra packets of yeast will just increase the amount of yeast to start so fermentation starts quicker. D47 from lavin is a good yeast for mead, along with 71b for some types of melomel are good safe yeasts.