1/no info by boeing
2/used by airbus
3/good enough
Few variables,main is to have an idea of your total track miles(base+final) to plan your rate of descent.
A visual normally gets you 5 miles,a circling is dependent on your height and the limit imposed by the actual visibility.
A 5000 m max visibility (2.7 nm) for a circling will mean that you will have to turn base around 2.2 nm,otherwise you will lose sight of the runway....depending on that factor and your circling height,timing may not be sufficient/acceptable to start the turn and you may have to increase your landing flaps to help with descent planning(lower speed/same rate..more time to lose altitude...)