@Tao,

With the recent smart plugs released, the scheduling feature is stored locally on the smart plug - however, having the connection cut out as the plug is executing the schedule could cause other problems entirely - meaning it should work, as long as settings don't go awry such as an out of sync time. For this reason we don't normally recommend this as a reliable use case, unless you are willing to test this function with your network configuraiton.

All of our current Smart Plugs operate over Wi-Fi, so there are no features you could look for beyond the local scheduling - which is listed as a supported feature on our spotlight pages and product datasheets. Off the top of my head, I actually cannot think of recent a model that does not support this function.

If you are able to maintain a Wi-Fi connection,and only your internet connection goes - there are a few features that you could try to take advantage of, such as the local communication via Matter with other hubs; or you could even consider taking advantage of the latest Tapo Hub and Smart Plug, which can use the the Local Smart Action feature of the hub to send commands from inside your network.

I would first make sure that your modem or router do not support an automatic reboot feature, as this is becoming a common feature nowadays.