newbie IPV4 vs IPV6 question

[opensensical]

Hello,
I am trying to set up a new opnsense box with dual WAN.
I noticed that the default WAN had both IPV4 and IPV6 support enabled, so I did the same for the second WAN.
I don't know if the two ISPs use IPV6 or not, so I enabled both in case they do.
Now, in all subsequent configs relating to the interfaces, IPV6 is now associated with the interface.
I also notice I now have 3 gateways (how did I end up with an extra one):
WAN_DHCP6 protocol IPV6 priority 256 description INTERFACE WAN_DHCP6 GATEWAY
WAN2_DHCP6 protocol IPV6 priority 256 description INTERFACE WAN2_DHCP6 GATEWAY
and WAN_GW protocol IPV4 priority defunct description WAN GATEWAY
Does opnsense fall back to IPV4 if no IPV6 is detected?
I saw a setting somewhere about having LAN track the interface, but with dual-WAN load balancing, how would I assign a single interface?
Can the network handle both IPV4 and IPV6 simultaneously if one ISP is on IPV4 and the other IPV6?