What does serial optimization do on the ConnectPort LTS?

This option can only be set via the ConnectPort LTS CLI:
#> set serial optimize=[throughput|latency]

Factory default is optimize=throughput.
If you set optimize=latency, the RX FIFO Trigger level of the serial port will be set to 1.
This option is effective in all profiles including RealPort.

Please note that if the baud rate of the serial port is less than 9600, then the RX FIFO Trigger level of the serial port is set to 1 regardless of optimize setting.