To prune or not to prune Exochorda x Macrantha and spacing.

I am fortunate that I have the “ luxury” of buying certain plants wholesale. Having a large garden I tend to buy plants in threes. I bought 3 Exchorda x Macrantha recently, a shrub I have never grown before. The plants are not substantial, a bit more than a rooted cutting but not exactly filing their 3 ltr pots. I intend to plant them shortly and not sure whether to prune back the stems that have flowered to encouraging bushing or not as the plants are still small.Also how wide apart would you recommend to plant them? My aim to to have a decent looking size within 5 years, ie I am far too old to wait 10 years for them to join up! Thanks in advance.