Your understanding is correct. How you choose a tracker is mainly related to your project.
The main difference between the two solutions is that with single tracker, you can track a pre-set number of targets simultaneously from the target set, but you cannot control which one can be always tracked even if it is in the scene, because the detect order is random. But with multiple tracker, you can assign a target to a tracker that always track one target, so it will always be detected and tracked when it is in the scene.
The multi-tracker solution has no performance impact compared to the single tracker solution. The performance is related to the total number of tracked targets only.