I use an empty, foiled water pan for most WSM cooks.
Regarding the bird/breast, I think the simplest way is in a roasting pan on the top rack. My roasting pan doesn't fit though. So plan B for me would be bird on top rack, empty foil pan on bottom rack. I'm not fond of the disposable foil pans, just because they don't have a smooth bottom - this helps with keeping the bird from swimming if it's in there, but creates a challenge when trying to scrape up the browned bits for gravy. (I have a rack for my roasting pan that keeps the bird off the bottom). I think I might try something a little different this year. Bird on rack in roasting pan on the Performer for an hour or so, just to get that cooked over charcoal flavor. Then pan and bird into the Genesis to finish just because it's easy to lock into a temp.