The tracks are angled and interleaved with the video, not at a right angle, which would be almost impossible and would require a second head drum- the HiFi audio, being FM and requiring much higher frequency range than linear analog recording could ever provide, works conveniently with the rotating video head drum and tape. However, Dynamic range for HiFi video recorders was stated as >80dB, about 16dB less than PCM in 16 bit mode.
If that reads like a sales pitch, it was- I sold video recorders and cameras, as well as audio. The 80dB spec is from the manual for a Sony SL-2700.