Regarding the out of trim status of the Q400
This is down to when you disconnect the autopilot as opposed to it always being out of trim on disconnect.
If you watch the aircraft in pitch on the glideslope next time you fly you'll see what I mean. As the aircraft is on the glideslope there is always movement in pitch to maintain the g/s as we change speed and configuration (obviously), invariably the out of trim status with the "jolt" comes when you disconnect the a/p as it is trimming for it's new state (even at Vref and configured) as it tries to remain on the g/s.
Before a/p disconnect wait until it is very stable then normally it won't happen. No aircraft will pin the g/s perfectly without a small or subtle "chase", even when fully configured and at Vref (but you already knew that
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