Most plants are not pruned or replanted until after they have bloomed. A rule of thumb for most things is to cut out any diseased or dead wood and crossing branches. If you are pruning a hedge and you don't want bare legs, you should taper the shape so that the top is narrower than the bottom.
Those shrubs are quite over grown. I would not try to prune off more than a third of the shrub or even less. Most shrubs have no leaves at all on the inside of the plant. I would just take out what is obviously dead, disseased and crossing. Remove the straggler branches and then do some reduction pruning by only taking off a couple of inches at a time. You can always come back and cut more off, but if you take off too much it will take a long time to fix it. Every couple of weeks you can reduce a little more. Pruning and feeding after will tell you how fast the plant grows. The ones that start sprouting new leaves will quickly rejuvenate and can take a little more pruning, the ones that don't grow as fast you have to go slower.