So you're starting to utilize Active Dataguard, and you want to check your explain plan against the your primary... I tried this through TOAD. No luck.. Most tools use a temporary table to store the explain plan then show it...
In order to see the explain plan use
select * from table(dbms_xplan.display_cursor('4nscfh7ef96z6',null,'typical +peeked_binds'));
This will work in ADG, and the primary to compare..
It will also show you the bind variable values used to resolve the plan.