Uncertainty Extended Tracking in HoloLens

Hello,

I have 4 Question, which I would like to hear the answer or an approval for my through about this topic.

I have an image target and the option Track Device Pose is not activated. Currently when the image targe is not in fov, the ar content still appear. That is what I aim for. 

1. So according to the information from here. From my understanding,even when I do not activate the Track Device Pose, HoloLens still use its own spatial mapping to track the pose of the ar content right ? (therefore I could see the ar content even when the image target is out of view)

2. What I really dont lilke is that the ar content is very lag. The gaze of hololens is not smooth when I aim to the ar content. is it because of the hololens hardware or because of spatial mapping in hololens?

What I discovered so far:

3. Ar Content appeared even when image target not in fov, but the ar camera still  turn on? Why and could I disable without problem to reduce the workload ?

4. So in conclusion: Especially in HoloLens you dont need to activate Track Device Pose from Unity, the extended Tracking behaviour is automatic set when you developt app under HoloLens ? If its like that, so currently I can see that HoloLens use spatial mapping to track and the ar camera also turn on, which mean vuforia also use extended tracking.

What I really want:

irrespective of whether extended tracking by vuforia or spatial mapping by hololens, the arcontent should still present when the image target is no longer in the field of view. If spatial mapping is used then the AR-Camera should be switched off to prevent the exposure. Conversely, if spatial mapping is not used by HoloLens, then vuforia should  enable Extended Tracking and only Extended Tracking will be applied.

Thanks