There may be a conceptual disconnect between the term Semantic Detection and the task of Head Tracking, since sequential recognition of an object in a set of visual samples representing continuous movement isn't technically a semantics problem. Although a mapping strategy that works with semantic processing may somehow apply to, with appropriate modifications, the mapping of obstructions and tracked objects and their relationship in space-time.
Tracking a head is primarily a surface fitting convergence problem, where the convergence goal and the process that achieved it must be sustainable, especially if the system is required to take actions during the tracking operation. Distinguishing heads from one another requires a high degree of reliability and accuracy in this convergent continuity. That is the primary challenge.
Drawing boxes and displaying counts are trivial operations once the head tracking works.
These are some models listed in the question or improvements over them.
- Fast LBP Face Detection on low-power SIMD architectures, Olexa Bilaniuk, Ehsan Fazl-Ersi, Robert Laganiere, Christina Xu, Daniel Laroche, Craig Moulder
- *A Real-Time AdaBoost Cascade Face Tracker Based on Likelihood Map and Optical Flow, Ranftl, Alonso-Fernandez, Karlsson, Bigun, IET Biometrics, 2017, Vol. 6, no 6, p. 468-477
- A Real-Time AdaBoost Cascade Face Tracker Based on Likelihood Map and Optical Flow, IET Biometrics, 6(6): 468-477
- A New Approach to Urban Pedestrian Detection for Automatic Braking, Alberto Broggi et. al. IEEE Transactions on Intelligent Transportation Systems, Vol. 10, No. 4, 2009
- Mask R-CNN, Kaiming He, Georgia Gkioxari, Piotr Dollar, Ross Girshick, Facebook AI Research (FAIR)
One seasoned expert spoke to a particular detail in the final question.
The thought process experts use to choose a model has no equivalent point value in StackExchange reputation. As experts retire, some may be willing to sell the professional heuristics they acquired over decades of research and development work if they haven't done so already to a book publisher.
Nonetheless, the above links are a good furtherance of the thought process begun in this question along a direction of continued effective thought. The following steps provide a road map for how to develop approaches in general.
- Read the academic materials until you understand.
- Determine your selection criteria.
- Test the options against that criteria.
- Pick the winner.
- If something blocks progress with that one, pick the runner up.