interactive talking head with emotions and speech

Seemless is a point of view. Shaders, lighting, and setup will still be needed for avatar import on ANY tool you end up using for your final product. Unity provides mecanim or code ability to get the animations, and lip sync setup as desired.

Unity can accomplish the task you desire, but other dedicated talking avatar tools can also accomplish this task. I've seen dedicated talking avatar tools on the market for over 10 years, in various forms of quality and complexity.
It'll be up to you to decide to use one of these tools or go with Unity which will not limit you, but require you to set up a system that works for your unique output. This is a common requirement for most game developers as well.

Thank you for your prompt response @theANMATOR2b . I have honestly not explored other 3D rendering engines as yet. My attraction to Unity is the fact that it seems to be built on Mono (like Xamarin, it is cross-platform), and provides scripting access in C#, which I imagine would allow me to dynamically manage animations, emotions, and speech input.

From the avatar creation end, I started looking at CrazyTalk 8, which seems like a good fit, but I am a little bit concerned about their product history and roadmap. I have quite a bit of learning ahead of me, so I am just trying to ensure I start out in the right direction with the correct toolset.