Characters with their health going below zero further than their constitution score die. There is an option (Death's Door) that gives them a second chance, and it's reset by resting in a safe place (like the capital). It's very rare to have a character dying 2 times before you can reset it, I never had this in Kingmaker on the normal setting.
There are multiple difficulty options to make it easier too.
The "random and not being able to load/save" part is simply not true. Unless you specifically select "Last Azlanti" mode, which only allows you one save file, so you can save your progress, but not come back.
The only issue is the kingdom management, but you can prevent bad decisions from destroying your kingdom with an option (there's an automatic mode but it doesn't work, unless they fixed it recently).
All that being said… if you play PoE and extensions, chances are Wrath of the Righteous will be released and hotfixed enough when you're finished, it could be a better choice than Kingmaker. To confirm once someone has played it through, to be on the safe side.