1. None of them, since Microsoft changes the table structures and internal details from time to time, and emphatically does NOT guarantee anything about those tables. The sp_helparticlecolumns stored procedure will give you this information though, in a supported fashion too!
2. Again, none, for the same reason. There are more choices for stored procedures here, can you give an example of what information you're trying to retrieve?
These questions are actually straight from a customer of mine who wants me to add documentation of replication related stuff to sqlspec. I've never used replication before so I thought I'd ask here. Premature.
thanks though. I'll come back when I have done my homework!