How does it work logistically when it is a separate unit from the toilet? Are you supposed to shuffle over from the toilet to the bidet with your garments open?
Yes. One might want to take care of the main stuff the usual way at least in part before passing on to the bidet, though, so as not to risk soiling. Source: Argentina, land of bidets.
Nope. Extremely impractical. Better and simpler to retrofit an existing toilet (preferred) or have a toilet that includes the function (very expensive in the US).