Never felt relaxed in Chieftain for some reason.
I flew a number of well maintained chiefs on mostly passenger charter and some RPT. They were always very reliable and safe. I know more than a few that are in pretty bad shape doing freight work and outback. That might be the ones you would feel 'at risk' in.
I did the endorsement back in the ole days where the instructor pulled the mixture and you actually feathered and landed 1 inop. It handled well on one engine, even had an air return on one engine with 10 pob at a later date. Knowing exactly how much drag an open cowl flap or such creates is critical at max weight, that alone could be the difference between climb, level or not. They definitely did not like hot conditions, very easy for those oil and CHT temps to build up if you stayed low on a hot day, and opening the barn door cowls would slow you significantly.