Here's what I mean, One track applied to multiple layers and effects. There is also nothing keeping you from tracking position, scale and rotation then applying only the position data to an effect, then using the same tracking data to tie something else to a null or another layer. What if you have two effects that have Point controls? Now you have to either put the one you want at the top or add them later. If you want to apply the tracking data to an effect you should select it when you choose the target instead of having the target chosen for you automatically. Having the data of an effect with Point Controls set to as the default and then not being able to deselect it before you track seems like a bug or at least a not very well thought out workflow. I almost always track first, then add a layer or a null and either use the null or layer as a target or tie expressions to the tracking data directly. It's actually the first time I have seen a user in the forums get in trouble for having effect being the default but in all fairness - there is no other layer in the layer stack anyway but that's my personal preference, I am not sure how many users prefer that. In the case where you don't have the another layer in the layer stack, and effect applied to the tracked layer - it defaults to the effect in the layer and not another layer in the layer stack - in this case I would support the default would be the other layer, and not the effect. In the case where you have the another layer in the layer stack, and effect applied to the tracked layer - the default would be the other layer if you do have another layer in the layer stack (before the tracking), it will default to the 1st layer, if you don't, it will default to the effect in the layer itself because that's the only option.
if you do hit edit target, the only reason it's enabled is that it has effect with position coordinates applied to the layer (which is kinda rare for tracking a video anyway).
How do you mean "disable the tracking"? if you don't apply to anything then it's not doing anything. You ought to at least be able to disable the tracking if you have an effect applied to a layer I do most of my motion tracking before I add another layer