The suggestions for narrowing the field of view on a motion sensor with a paper tube is easy and effective. It will work well with this Centralite or this Sylvania.
Zigbee device and the hub will be on the same frequency when they are joined together. You can pick a frequency that doesn't interfere with you WiFi if you need to. But it's often easier to change your wifi router channel if needed. Certain Zigbee devices will prefer certain channels. This is not that common, but there are a few exceptions. I use channel 13 on my hub. I didn't choose it, but have never had problems with that channel and any device, or with my WiFi conflicting.
There is good info about Zigbee and Z-Wave in the docs.
Not sure how gesture control might be interfaced. But you may be interested in something like HubDuino for different types of unique inputs and outputs.
