Two 6in4 IPv6 WANs, how prefer one?

Hi all
Since my ISP only gives a /64 network (with 6in4), I have opened a /48 from Hurricane (still 6in4). I want that normal traffic use my ISP WAN, while HE should be used only for particularl scenario (ipv6 openvpn and NAT64 ). But my devices get global scope ipv6 address from both networks, and according to traceroute6 they use HE WAN for outbound traffic.
So how can I make these device to prefer my ISP WAN? I mean devices in NAT64 and Openvpn will get only HE addresses, but I need the devices in my LAN, that take both, to prefer my ISP WAN. Is mwan3 the answer here? Or something else?