I would like to hear an official ESRI reply to this, but a few years ago, I was told that it is possible to edit traditional versioned data with SQL, as long as you follow the rules (there are a couple of procedures to get an appropriate ObjectID, and GlobalID value are a couple of big ones but there are others). Also they warned against editing the same table or feature class both through SQL, and through an ESRI Client application. My understanding of that is not all supported DBMS systems support shared ObjectID retrieval between processes so you may get undesireable results if you edit the same table with both types of clients. Also advanced Geodatabase functionality (Topology, Network Dataset, Attribute Rules etc.) are not supported when you edit through SQL, so you have to be careful how you design your Geodatabase. All that being said. I have successfully edited a traditionally versioned feature class through SQL but I recommend you fully understand how traditional versioning works and really evaluate your database design before going too far down this road. I have not needed to deal with Branch Versioning at this level yet, but Branch Versioning is implemented very different than traditional versioning.
