Sorry to hear that had problems interacting with the environment sometimes, I'm glad you liked it though.
As for your questions:

1. The models used are from a pack (kaykit). Used the fbx. The usual import in Unity works well by dragging the models into the inspector. There is a thing to take in consideration though when importing models from blender, because unity uses Y as vertical axis and blender uses Z. there is an export option in blender to fix it though.
2. For the camera, not that difficult to implement it with Unity. There is a Unity package called Cinemachine that makes camera managing quite simple (can do follow cameras, orbital ones, third person "over shoulder", transitions like in old RE games, split screens and lot more)

For the Godot-Unity, I've only used Unity and has a lot of packages that can make things easier but there's the issue of knowing about all of them. I want to try Godot too, but finding time is hard XD