VOP (VEX Operators) are actually just nodes that generate VEX (Vector EXpression language) code. That right click operation spews the code into an ASCII .vfl file, which is not the most user-friendly code available and you probably won’t have a very nice time parsing it. VEX was originally designed as a shading language, but like everything else in Houdini, it works with anything Houdini can make.
The point is, VOP-based VEX nodes and shaders are just as fast as coded ones (faster sometimes), but if you must have code, you can prototype your thing in VOPs, and make an equivalent .vfl file with your nice, commented, human-readable, version-controllable code.
I could see doing something similar in Blueprint, but it would really be nice to have a document that maps each Blueprint node to its corresponding C++ class/struct/function, etc. Maybe there is one and I just haven’t found it. Such is the lot of a UE4 noob.