@Tim-Black 

Hello, if you or friends want to distinguish the two extender networks, you may create two different networks. If that is not necessary, then you can keep them the same.

Generally, the clients will choose better and stronger signal wireless automatically, but there might be short disconnect-reconnect behavior on the clients when roaming, which is obvious when doing the Wi-Fi Calling.

For a wireless device roaming issue, you may refer to this FAQ below:
https://www.tp-link.com/support/faq/592/

May it help.

@Tim-Black 

Generally, when a client or device is moving around between the main router and the extender, it will choose to connect to a better wireless signal automatically and you may even hardly "see" this disconnect-reconnect process. However, some special applications such as Wi-Fi calling or video calls may feel this small and short disconnect-reconnect.

A mesh network such as Deco mesh or Onemesh network may help a lot in such situations if you have a high requirement for the roaming experience.

May it help.