I want to install a tablet-only game via the play store, and I am at the build.prop file, only I don't know what to change the device to - does anyone know what values I can put in for the ro.product.name and ro.product.model for a new-ish tablet? something along the lines of a galaxy tab s for example?
You CAN'T just change the model number/name. What you have to change is the DPI setting of your phone for this specific app.
For that, follow up this explanation to do so with XPosed: http://highonandroid.com/android-apps/how-to-run-apps-in-phone-or-tablet-mode-on-any-rooted-android-smartphonetablet/