Is there a single document that talks about what's different in
automated installs for 7.0 and 8.1 ?

I've found

It's not clear if, say, a 7.0 silent.xml will work in 8.1 (though there
are some similarities) I do see that what we used to do to invoke it
has changed, we used to do something like
\common\lib\dmwiz.jar" -mode=silent -silent_xml="%DOMAINXMLFILE%"

and now it seems that config.cmd will do something like
%JAVA_HOME%\bin\java %MEM_ARGS% com.bea.plateng.wizard.WizardController

Thanks for any pointers...