limbot
7
Fing does a scan across the whole network for all devices, you’ll see routers, access points, end devices like printers, phones and it’ll give you the name and MAC address of all the devices (if I remember correctly I haven’t used for a while). So if you say connected your 6 devices to the public WiFi, all those devices could easily be “found” by other people on that network and potentially a malicious actor could try and gain access to your devices.
If you sit behind your Beryl, as @groentjuh says, you have a firewall between your 6 devices and the rest of the network. Someone doing a Fing search would only see your Beryl, but not all your devices behind the Beryl. The firewall protects all your devices from being seen and accessible to anyone else on the network. The VPN would then also protect your data by encrypting it. It’s another layer of protection 
You can do month by month with Mullvad, so no long term lock in contracts, so worth giving a go. They have an article here which might explain VPN better than I can 
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