Error: cannot convert argument 2 from 'FString (__cdecl FMyClassDetails::* )(void) const' to 'FString (__cdecl IPropertyHandle::* )(void) const'

ObjectPath takes a pointer to member function of IPropertyHandle but you are giving it a pointer to member function of FMyClasssDetails. If your class actually inherits from IPropertyHandle you can cast it like so:

static_cast<FString (IPropertyHandle::*)() const>(&FMyClasssDetails::GetModelPath);