Regarding this configuration of yours, it would be best to test it on an actual basis. For the wireguard configuration, you can refer to this link: WireGuard Configuration Example - Teltonika Networks Wiki (teltonika-networks.com)
But for the traffic, you want to separate the two IP address range I believe you can do it in Network > Firewall > Traffic Rules.
For more information, you can refer to this link: RUTX09 Firewall - Teltonika Networks Wiki (teltonika-networks.com)
Just create a rule that when the said IP address is going to access the Gateway for Wireguard packet will be rejected and allow the communication to the ISP side (WAN Side).
I hope it helps