Please check the LAN and WAN subnet of the two devices. For example, the IP of device 1 is 192.168.8.100 and the LAN range of device 2 is 192.168.8.0/24, which will be in conflict.
WireGuard supports access to other clients, but S2S does not provide quick configuration for this. You have to modify the WireGuard configuration file manually.
In addition, mentioning that S2S has modified the WireGuard configuration after the configuration file has been manually modified may result in unintended consequences.