Cytisus Broom loves to be planted in full sun and will reach approx 1.2 m in height, I would call it a medium sized shrub. It is a hardy evergreen shrub with pea like flowers.
The spread is about 1.5m, so I wouldn’t plant them too close together, if planting more than 1, give them enough space to spread their wings, 1.5m is approx 4 feet.