It looks like AGM's tags do not update on each frame, resulting in more jittery tags. I think option 3 may be the best since we're all used to them. However, I do have a question regarding name tags in general, this is aimed at everyone:
Currently, name tags only appear when you point your weapon directly at another unit. If you move your head and look at another unit (using TrackIR or just with Alt), their name tag won't appear. Also, similarly to what ST HUD tries to simulate, in real life you have a situational awareness of who's within your peripheral vision/around you.

To give an example, in this screenshot we can see 4 friendly units (2 far left & right, 2 on the right side of the road). In real life, you would know who those guys are since we're able to recognize people by their face and/or body shape*, even from afar.
So here's the question - what do people think about having name tags above everyone's head (in a non-obstructive way, that doesn't break immersion) within a 30m radius (ST HUD range)? Name tags could fade the further away a unit gets from you.
*Source:
http://www.dailymail.co.uk/sciencetech/article-2443731/Recognise-friend-far-away-Your-brain-probably-analysing-body-NOT-face-reveals-study.html