When you bring in those files as keyable elements, you are basically bringing in a nested clip within Avid.
Key channel, fill channel, and a matte key effect added on top.
Double clicking it simply reveals the key and the fill.
If you want to alter the speed, or the size of one or both, then you can either double click to expose the workings, and add your effects to them, or you can actually drag the items out of the container, and place the tracks beside each other on the timeline. Note, bringing the first item out is pretty straight forward. Bringing the second item out could cause your timeline to ripple as the empty matte key container will be deleted, and Avid will want to fill in the space…just be aware. Some situations dictate alt dragging the clips out instead.
If you do remove them, do your adjustments, and then stack them on top of each other…matte on top I believe…and add a matte key effect back onto the matte clip. (depending on the matte, you may need to invert the key.)
It wont be as concise, as it will now occupy to video tracks, but it will work the same way.
Glenn