Premature Optimzation??
A coding guideline exists. (dated to 4.5)
The Blueprint Best Practices has not been published yet. It’s description is “When to use Blueprints vs C++, Dos and Don’ts, tips and tricks, etc.”.
Hopefully both will be updated/ship for 4.7 release.
Also, if you’re unaware, if you go into Editor settings and add a key binding to Blueprint Editor->Generate Native Code(Generate C++ code from the blueprint) you will be able to get an easier idea on how to convert your Blueprint into C++.
I think Hourences videos would give you a better sense of UE4: Hourences.com – The Solus Project
BP and C++
Series 2 part 2 (miss labeled part 1) at around 4 minutes, or jump to 9:20
Series 1 part 3 at 5 minute mark.
Hopefully Epic will invite Hourences to Inside Unreal to give a post mortem after they ship.