Depends on the carpet, the vac power of the machinery and if the wand has a glide on it.
Even with the TM I can wand one-handed no problem on low profiles - on bigger jobs it's nice to switch arms regularly to save fatigue. But on some domestic carpets like cut pile polyprop that is matted down, you need two hands definitely.
Posture is very bad for me with wands because I'm so tall, I have to stoop to use the grab handle, or if it is set high enough it is too far away from the wand head to give me enough leverage to be of any use. I'd hold the tube but it gets a bit hot
