This option is supported by 8-series and 9-series powerline devices only. It can lowerthe interference to the VDSL device, but may reduce the data transfer rate. Use thismode only if the performance of a VDSL device is being affected by your powerlinenetwork.
However, this function is only for powerline devices which support mimo. The TL-PA7020 has no mimo function and it will not interfere with VDSL device.

This option, while neatly labeled "interference reduction" simply disables MIMO. It "may" reduce the data transfer rate by half. Of course, if your PLC doesn't have MIMO to begin with, there is nothing to do.

The proper way of reducing interference is in the cabling. When your house wiring runs the phone wire in the same pipe with one or more power wires, AND the phone cable is unshielded, then PLC will radiate into the phone line. Two ways of solving: Wire this properly, phone wire in a separate pipe, or at least pull that unshielded phone wire and run that length through a well shielded cable. CAT.6 Ethernet cable usually does a very good job.