Would look at this note :
Data Guard Support for Heterogeneous Primary and Physical Standbys in Same Data Guard Configuration [ID 413484.1]
I believe it will answer most questions.
Agreed - the document will answer your question in full detail.
But the short answer is that for a physical standby as long as the OS endian format is the same and the version of Oracle database is exactly the same then you should be fine. If the OS endian changes or the Oracle RDBMS version is different then you'll need to go with logical standby.