The word you're looking for isn't sentient but sapient.
in simple terms:
Sentience = Intelligence.
Sapience = Emotional Awareness.
It's more complicated then that but yes, Sebas is one of few truly good aligned members of Nazarick. Thus one of the few who feel empathetic to regular people.
As for Ainz not being the focus I think that's kinda the point. This season is looking into the grand plans of Nazarick as a conqueror/ruling force, as well as their impact on the world overall. So we get to see the world reacting to Nazarick and it's actions. I like it
The Force
2022-11-05 19:43:15 +0000 UTC
Honestly I love s2 of overlord I think if an anime can move away from its main cast and the world still holds up and life continues that's good world building