But you don't need to configure wireguard on the individual devices just on the openwrt router. That's one device and you can keep that on permanently.
Except that sometimes you can’t. I don’t know if the Unifi router checks for this, but I’ve run into more than one network where the VPN conflicted with either the captive portal or the wireless network itself (and at least one in the DFW Admiral’s club that had draconian blocking)