the 1600 on a b350 will OC just fine. It's quite easy to do. Just keep in mind on the stock cooler, people are having trouble getting the 3.9 mark. It's just too much for the wraith spire. Some people have been lucky and gotten there with reasonable temps, but that depends on the chip itself. 3.75-3.8 is more easily reached. At 3.75 it's plenty powerful to drive the 1080ti with no bottleneck. You may eek a few more FPS at 1080p with other chips (I7 7700k etc), but once you go 1080p 144hz, 1440p or above the balance shifts to the GPU, and the Ryzen performs almost as good as any chip you care to mention, except maybe the 8700k/8600k where the IPC of those chips will give a few FPS increase, but the Ryzen will be damn close. Much closer than at 1080p @60hz, where it's all about clockspeed and IPC.
There are a few recommended B350's. MSI B350 Mortar, Asus Prime b350 Plus (my one) The Asus B350 Gaming is another.
They are all very similar, and roughly the same price.