How do you all manage character head movement?

1. It lists files such as YourPlayerController.cpp.

YourPlayerController.cpp as in the player controller that you are using, what ever you’re calling it.
e.g. ShooterPlayerController.cpp, FirstPersonPlayerController.cpp, GBPlayerController.cpp

2. Is there a way to toggle mode on and off or to have it has a ‘hold down to activate’?

It can be set to toggle (on/off) or be momentary (hold on, release off).
Just depends on how you set everything up.

3. Template or just start from scratch?

The quick VR test project I created to test various bits of code was based on the third person template.
It needed a player model and it isn’t hard to alter the third person movement.

4. Prefer C++ over Blueprint?

I do all the classes in C++ and then use Blueprints to flesh them out.
is a pretty typical practice for UE4 - check out the shooter or strategy examples.