It depends on what bulbs you get. One should be uva(basking) and one a UVB like a 5.0. Some bulbs come in a combo, but again that would depend on what bulb you purchase. Bottom line is you need both uvb/uva.
That really depends on a lot of things starting with the species and the ambient room temperature. Right now, I don't have any basking lights. The Arcadia quads throw plenty of heat, and for most of my collection, reducing temps is the issue.
In the winter, I might put a basking light for the veileds.
The lights themselves do get pretty warm, all HO flo. (HO= High Out-put)
But no Flo. light will project heat downward into a cage the way an incandescent bulb in a dome light will, so the answers above are all correct--
IF the room is pretty warm any way and the top perches in the cage are 86 + - then you would may be ok w/o
But personally, I would not go w/o a basking light -
just adjust the wattage of the bulb.
Use a 25/40w bulb in a 5.5" dome in summer and a 60w bulb in winter, only on during the day. The temp on the basking perches should be 86+-90-ish.
Coldblooded animals need heat to properly digest their food- so a basking light is always a good idea even if they don't use it all the time.
I think it is important to their health that they have that option.