There's no mention of Output Management Web Viewer in the processor compatibility matrix.
Can you pls confirm if v14 and v12.1.6 build 218 are ok on z16s?
There is no 12.1 Web Viewer processor compatibility statement because, it runs as more of distributed application than a mainframe one.
For 14.0 Web Viewer however, Broadcom creates a single matrix across all products for z16 compatibility - IBM zEnterprise Compatibility Matrix
and search for View/Deliver 14.0.
Web Viewer 14.0 is a component of View.