My bad for misreading what you wrote and i must apologize for that.
In the case for the wonky IAS climb behavior. I’ve sat on the jump seat thrice before and i noticed the crew rarely engage it that early until most of the workload phase have stabilize.
What i noticed they would do for take off and climb.
Rotate out at v2 onwards pitch it between 8 to 10 degrees but never more than 10degrees.
Positive rate gear up.
At around 200 feet engage yaw damper.
At 400feet(may wary depending on the airport your operating out of it may be higher) is the typical acceleration height and they would pitch it to 5-6 degree let it climb very shallow and trim.
Set engine power management to climb.
Let the speed go past flap speed and retract the flaps.
Engage autopilot.
Use v/s +1000fpm until 160knots or approaching 170knots only then ias climb is engaged bugged to 170knots.
Was also told by the crew if the airport is surrounded by mountains and they wanna climb the hell out of it. They would opt to climb using IAS climb at white bug +10knots which is usually around 140-150knots for a steeper climb until satisfied they would use back v/s +500 and let to the speed go back to 170knots and reengage IAS climb at 170.
A bit different from the Boeing and Airbus where they can just turn on the autopilot at 200feet and let the plane settle itself and only move the flap or thrust(for airbus) lever position based on speed and acceleration height schedule lol. The LVL change/FL CH and Open climb/descent is also a lot more stable than the Atr.