How many datapoints the S7-TCP driver is able to deliver within a second?
It depends on many factors:

1. SPS -> the S7 protocol uses a maximum paket size of 256 Byte ( aprox. 200 Byte real data), which are delivered in one transmission.
2. Cycle time of the SPS -> One request (max. 256 byte) is available within one cycletime.
3. Netzwerk -> The transmission depends on the network itself
4. Datatype (Bool, INT, DINT, REAL,) -> 20000 bools are far less data to transmit than 20000 REAL variables

At the beginning you should know how much data (byte) is to transmit.

It takes typically 50 ms till one paket reaches zenOn, which means 200 * 20 = 4000 Bytes per second maximum.
As an idea aprox. 32 000 Bools, but only 500 REAL (8Byte) variables per sec.