Ok, thanks to all !
UpperCamelCase seems most widely used, this is what I thought.
When you think, that’s logic, Unity doesn’t have a clearly defined Naming Convention, unlike C#.
Properties are meant to look like fields, so I just use the same naming convention for both. That said, naming private properties with _underscoredLowerCamelCase feels odd. Still, private properties are rare.
I use the Resharper naming convention which is UpperCamelCase for public / internal / protected and _lowerCameCase for private and I do this on fields as well as properties as they are meant to be the ‘same’ to the outside