Attempting to start without forgetting to turn off other battery sucking items like cabin comfort control leading to insufficient battery power for start?
Not familiar with the Meridian, but have flown other PT-6 powered machines. Is cabin comfort control electrically powered or does it use bleed air? If it uses bleed air, is the valve opened/closed electrically?
I'd be surprised if you have done any lasting damage, but you are wise to have it inspected.
The smoke is mysterious, and the only similar instance I can recall was when having to shut down a PT6 using the fire shutoff (but no extinguisher) due to an issue with the fuel control unit. That created lots of smoke, but no damage.