The Adafruit ItsyBitsy headers are great. Though connecting VUSB might be an issue.
However, I find the Sparkfun stacking headers for the Teensy 3.2/4.0 to be less useful. The ItsyBitsy headers are 2 14-pin headers and one 5-pin header. The Sparkfun headers are 2 13-pin headers and one 7-pin header. For breadboarding, etc. I find it easier to use a stacking header for the back 5 pins (or solder in the stacking header, and just clip off the pins). In addition, the 14-pin headers work better on the Audio Shields (which don't have the back row of pins). I presume it would also work better for the Octows2811 shield, but I don't use that.