Question about TP-Link TL-WPA7517 KIT

This is also available, but for a good WLAN and good coverage I would rather invest in a mesh system, a very good and inexpensive WiFi 6 mesh system is available from Xiaomi, for example, the AX3000. It comes with two mesh routers, each with a 3-port Gbit switch and a WAN connection, which you would connect to the provider's Internet router and then set up the second mesh device a little further away, so that you then have WLAN in the entire area and can move freely without the WLAN breaking (this is often the case when you use range extenders).

However, the TL-WPA7517 only seems to be available as a set at Digitec.