Yes, a dwarf size would have been better for the long run. Many people plant Gold Mop when they are young and small. 

Now is not the right time to prune. Next mid-late March would be better. You can try to do a rejuvenation/renewal prune on them and see if they regrow, however it will be a maintenance task down the road to keep them small. It will also probably take a few years to regrow, and since the inner branches look quite bare, they may not push new growth. You can reference the following Youtube video that is helpful to learn how to perform a rejuvenation prune. 

You could always attempt the prune and if it looks too sparse, you don't want to wait for it to regrow, or they fail to grow out, you could remove and re-plant with something smaller. After you do the hard prune, provide water as needed and you could use some light balanced fertilizer to help it push new growth. Something with the nutrient ratio of 10-10-10 and 'slow release' would be good. 

Let us know if you choose to replace and would like suggestions on plant replacements, or have any further questions with the pruning. 

Emily