You don't have to buy a new computer to get Wi-Fi 7 speeds. There are external Wi-Fi dongles, such as the Asus RT-BE58 Go or Acer Wave D7, that you can plug into an available USB port to get Wi-Fi 7 ...
One type of electronic device to especially avoid is the microwave, which emits a strong signal in the 2.4GHz band, the same wireless band your router operates in. Be careful not to stick your router ...
On your old laptop, download the Spacedesk Viewer app. Launch the viewer, and it should automatically detect your primary PC on the network with its IP address listed. To set it as an extended display ...