Attila Total War is a terrible game to test anything with.
The Game Devs have made a total mess of it and then to get out of jail they have said it is too demanding to run on any current hardware with max setting.
In reality the game devs can not be bothered to get it optimised and ensure that C/F and SLI work too. This is not something that AMD or NVidia can be blamed for as it is purely down to the game devs.
Exactly the same happened with RTW2 when it launched and the game devs still have not got that sorted entirely either on both brands.
Its built on 'Warscape Engine', which is ancient; and a dog even in its day.