About the Pass labs x250.5 meter & Class A output

I recently got a x250.5 and just had a few question. I've auditioned a few pass labs amps in the past, and have seen what the meter looks like when it's really bouncing. At my current listening level (~90dB) the meter seems to move every so slightly in place; if the meter is normally at 11:00, it bounces back between 11:00 and 11:10 at most. Does this mean that I've left Class A, or do you only leave Class A when the meter is really bouncing? I know there are some threads about this, however there are always multiple different answers; no consensus.

Also, it is stated that X250.5 is biased to output the first 15 watts in class before it shifts into Class A/B bias. Does the 15 watt figure double down into a 4ohm load, or does it remain 15 watts of class a regardless of the load?

Lastly, has anyone ever gone from the x250.5 to the xa100.5? What kind of differences did you experience? Do you prefer one over the other?