A track clone refers to a voice clone that is derived from the entire track in a dubbing project. This means that the voice clone will be made from a combination of all of the clips on that track. This is the default behavior and is good for creating voice clones that have a bit of the characteristics of all the clips combined and usually give the AI enough data to create a proper clone. However, if the voice changes quite drastically throughout, it might create a voice that is a bit more unstable.
On the other hand, a clip clone refers to a voice clone that is derived from a specific clip on a track. This allows you to create different voice clones from specific clips and assign that same voice to other clips where you want the tonality or performance. This can be great if you feel like a specific track has exactly the performance you want and want to apply this to other clips too, or perhaps, you want to apply this to the whole track.
One helpful tip mentioned in the content is to find a clip that you like, where you feel the voice is good, right-click to create a clone from that clip, and then assign that clone to the whole track to achieve a consistent voice throughout. This is just one tip and may not work for all circumstances, but it can work very well in some cases.