Trouble with Vuforia's version

Hello

I'm currently trying to develop an app for HoloLens using Vuforia

I manage to do a small app with Unity 2017.2.1f1 and the legacy version of Vuforia (6.2.10) found here : https://developer.vuforia.com/downloads/sdk

On this app, I manage to do the image recognition and put a cube on it, but the thing is, the hologram is not stable , not fixed to the image target. It seems like everytime I'm moving my head, the hologram is following the movement. Also, it appears that the holograms is kind of half inside of the image target, even if in Unity i've put it on the top of the image target.

I tried to make a new app using Unity 2018.1.0f2 and Vuforia 7.1.31, but I don't really understand of to make the app, as tutorials from the website are not up to date and Vuforia Hololens Sample are not working on my computer due to an error on Unity's editor. For instance, I don't know if I still need to have the MixedRealityCamera and the ARCamera from Vuforia to be able to track the image target.

On this case, when I tried to export the app on the Hololens, the light camera of the Hololens in front on it isn't turned on, compare to the project made with Vuforia 6.2.10 when I can track the image target

I would like to know what is the best version of Vuforia for making Hololens apps, or is there any up to date tutorials, because Hololens sample are not working and nothing is explained :/

Thanks a lot for your answer