Hi Kat, Kimberly here from landscape-solutions-for-you. Thank you for asking your question on pruning your Yews and Junipers.
Both of these shrub specimens can follow the general rule of thumb of properly pruning in fall, or early spring. These are evergreens and the main objective in late fall is to prune before they begin slowing down their winter growth pattern. You live in a zone where the ground freezes, but you can even prune after your first frost. Once these two plant specimens are established like yours are, you can maintain their growth and health by actually pruning twice a year. The Yew and Junier family are very hardy and durable when matured. I have pruned my clients either in late fall or early spring. If the weather is rainy or a lot of snow in the winter months, if you have pruned in fall, go ahead and prune in spring after the new growth is established.
Go ahead and prune back and shape as desired now. Many Web sites have different opinions on pruning, but as a professional landscaper and designer, unless I know of a specie that requires pruning after flowering or a specific time, I recommend pruning in the fall or early spring. Your main objective is never to prune a shrub until new growth is well established.
I hope this clarifies your pruning issue and thanks again for asking the question here at landscape solutions for you. Feel free to ask a question anytime. Have a great day.
Kimberly