Heatmapping advise

Hi!

I've tried reaching out to Hikvision themselves but so far no luck so i was wondering if any of you guys might have some advise.

i am looking into DeepInView camera's that support queue management, heat mapping and so on. I've got a retail store in which the store height is 6m so i thought several top down camera's would be great for this but i'm not sure what keep in mind and which camera's to choose and how much overlap there should be.

Any feedback would be much appreciated!