Despite the closed monitoring circuit I have at home and at the office, I have also purchased 3 Xiaomi cameras. They always function without ever being disconnected in the last 3 years. Of course, they are connected to WiFi mesh (only connected to 2.4GHz, not 5GHz). Before the mesh, I constantly had disconnections, even on my mobile phone, due to the long distances from the router.
I read from other users that if you don't pay a subscription, Xiaomi doesn't send you motion detection notifications. I haven't noticed anything like that. The notifications work perfectly fine even today, although I don't know if it matters that I have an SD card in each Xiaomi camera.
The minimum time between notifications is 3 minutes. That means if it detects more than one motion within a 3-minute interval, you won't receive further notifications.
I have also set it to save recordings to a network disk (NAS) that I have, so there is no limitation on the volume of recordings.
You can set a password to access the camera (Face ID also works, at least on the iPhone).
I consider the image to be very satisfactory even at night.
Another positive aspect is that you can set automations, for example, when it detects motion, it can activate a light or any other smart device connected to the application.
I highly recommend it.