As most others here will agree, full height boxes are the best form of support. I can build one in the same time as an angled Strutt, as I find cutting the angles and mortice neatly and correctly is quite time consuming as well as getting the strutt and stob tight.
I can drive the second post of the box in and know that the horizontal brace or Strutt will always be tight and I can carve out a mortice with my carving saw using the jigs I have for marking, quicker than fitting a normal Strutt. I use a small dewalt laser measurer to put in the back of the mortice and shine it at the back of the other mortice to give me the exact length of the post/Strutt which makes it possible to do on your own instead of trying to hold a wobbly tape measure especially on deer fencing.
The only difference in cost, is an extra post but a lighter shorter strainer can be used. The amount of 2.5mm ht line wire used for the stay or brace wire is minimal and either a crimp or gripple to tension. I don't like gripples personally, and instead always use crimps and then a couple of wraps on eac end wit the tail and then do your breaks.
G PAKS are a complete waste of time and money. Gripple tools seem to shred the gpak cable very easily too. Use 2.5mm HT wrapped twice round.
Doing it this way they never seem to move or the stay wire go slack. I have visited boxes years later and the stay wire is still super taught.
My latest deer height boxes use a 3.6m machine round pole and I have a 100mm forstner bit in my petrol drill which creates the best fit imaginable and the most contact/bearing surface possible.
Most of my fencing is deer fencing. So all of it is a box of one description or another. I do use half height boxes with a stout deer intermediate for the inline strainer just driven much deeper and another for the horizontal strutt. They are pretty strong but not like a full height box.
They are sometimes useful to support a turn post built sticking out exactly half of the change in direction.
Usually i use half height boxes to exclude deer and proper full height boxes to keep them in.