Unfortunately you mix up the terms "Office Web Apps" and "Office Online Server". So it is not absolutely clear what you want to set up. I assume that you want to set up OfficeOnline Server and not Office Web Apps.
"Office Web Apps Server" is the product for the 2013 product family. It has been renamed in it's 2016 version to "Office Online Server"
This blog says, it works in "some scenarios". The Office Online Server version compatibility list says "Not supported". You shouldn't set this up in production.
My recommendation: Set up OfficeWebApps2013 for Exchange2013 and OfficeOnlineServer2016 for SharePoint 2016. You don't have to spend extra money on licenses and the hardware-footprint for those two servers is relative small.