Regarding NG A/T and A/S control, generally:
When I was a newish pilot on the NG, the following happened on two separate occasions, with two separate pilots, while I was PNF:
We were descending in LVL CHG (A/T in ARM mode) below 10000 feet while on vectors for the approach. For some reason the A/P was disengaged, and then the PF began manoeuvring for a visual approach (we were high on profile on one occasion). I remember the cockpit getting busy, and there being momentary confusion on the part of the two PFs as they looked down and saw the speed dropping (perhaps in response to call of mine, or not; too long ago to remember) below target.
They had not immediately realized that they were now MANUALLY controlling the T/L's, and were definitely caught off guard.
From those occasions, it reinforced a previous Airbus operation SOP about not using LVL CHG below 3000' AGL, IIRC. If using V/S at the time, and A/P is disengaged, the A/T will remain in MCP SPD mode.
Of course if APPROACH (for an ILS) mode is armed, upon G/S interception (Post LOC capture) the A/T will be back in MCP SPD regardless of A/P status.