I was hoping you were going to say that it uses something like MQTT to communicate, in which case you would have been able to get data hundreds of times a second before you ran into problems with node-red. Sorry, I don't know anything about tplink smart home so I can't comment on how often you can poll it. You are not going to have problems with the node-red end of it unless you poll many hundreds of times a second.
This ongoing thread might be of interest to you. How to compare 2 data sets with either an integral or derivative
