Deutzia 'Chardonnay Pearls' looks similar and has opposite leaves.

Yes! That looks correct. Thank you so much!

Looks like current to me too. Most likely alpine current which is grown for an ornamental use unless someone planted a current variety there for the fruit (like Red lake, rovada ect) which make mighty fine current jelly.

Currant is a plant that as a landscape shrub has a limited use. As you've discovered, it's prone to some foliar problems, and there are a couple of insect issues that can arise. However, these are merely cosmetic blemishes, merely making the plant not look as great as you'd like it to. Something capable of outright killing this plant? while those problems do exist (as they do for just about anything alive), they are rare. When it comes to pruning currant, as a hedge, as they were planted before they were yours, they are quite forgiving. Also, these are established plants...so first, they are forgiving in nature when it comes to pruning (meaning, go ahead, do your worst...the only thing you have to lose is something you don't like), they are also plants that have an energy reserve in that root system. So yeah, go head, do your worst...uhm, best. You'll learn something, and you'll have done it yourself. The whole first year, second year, third year pruning thing is a little different than what you are looking to do. That's for size reduction but still keeping the plant is good shape. also, pruning for fruit production isn't really what you are looking to do. I commend you for doing some background in how to prune. Now I want you to forget it, don't worry about knowing everything before you do anything, and to in part, learn by doing. A little studying is good, a little practical experience is good...then after a little hands on, go back and read again...you'll see things with an entirely new understanding.