Well... if you have my book, then there's not much more I can add... and if you've read the other thread about the Twelve Bens, then that should leave you in no doubt about what's inolved. On clear days, you can do almost anything. When the mist is down and it's lashing with rain, it's pretty miserable and you have to be very careful with navigation. The Harveys map is the best map. No other maps come close, but you need to be able to navigate, because a good map on its own is no use.
Wild camping is usually OK on the gaps between the mountains, except in the case of the gap with the chapel on it in the Maum Turks, which is accessible by 4X4, so you could be told to clear off. No-one will bother you on the more remote gaps. Just bear in mind that pegs don't go into hard quartzite, no matter how much you clobber them! As for water, last time I looked there was too much of it! I can't imagine ever running short of water in Connemara!