It sounds like you're thinking of LoRa, another 900MHz radio protocol.
LoRa has similar bandwidth to Zigbee (125kbps), and as you say is designed for low-power devices running on battery. I have PIR motion sensors at home which have used only around a third of their battery after 2 years.
Security cameras seems to be a large target market for HaLow though, where you need a couple of megabits at a few hundred metres.
Sometimes there's only a single PCIe lane though. And as you say, that's not a x2 but explicitly two x1s.
No WiFi card needs the bandwidth (yet), at PCIe 3 speeds you've got around 7.8Gbps for a x1, and PCIe 4 double that.
The Coral comes in a "dual" version for exactly this reason (https://coral.ai/products/m2-accelerator-dual-edgetpu/) you just have to be very sure the slot you're putting it in is actually delivering two PCIe connections.
Also for bonus fun, most WiFi/BT cards use the PCIe interface for the WiFi and USB for the Bluetooth.