I have noticed that the b350 motherboards are slightly slower than the x370 boards but also are you using a fresh install of windows 10 or are you migrating. Also what is task manager saying your speed is at. I would really suggest an ssd or m.2 if you want to have a faster system. I haven't used the wd blacks but the blues are very slow even a hybrid drive would be faster.
a SSD will speed up most of your applications