Which one for which room
The warmer ones, Gstaad Glam and Moon Paradise, suit a living room in winter. Tulum and Ibiza are lighter and greener and work in a bedroom or in summer.
A candle scents the room it burns in and nothing beyond it. If you want a whole floor to smell of something, a diffuser does that and a candle does not.
As a gift
A candle is the safest object to send to a house you have not seen, because it takes no permanent space. Pair it with the Assouline book of the same destination and the gift explains itself.