WAN CARP or NOT

[opnsense@f2f10.com]

HI Guys,
https://docs.opnsense.org/manual/how-tos/carp.html

Based on above link, it seems that we need CARP for LAN, as well as for WAN.

If I have each separate internet connection to each separate opnSense box directly on the box, those two IP from provider would be like, 1.1.1.1 and 2.2.2.2, which are not on same subnet.

If I have to do as what documents said, I would either put provider equipment in router mode and configure it's internal interface to 3.3.3.x, which will be for both provider equipment internal interface , as well as two OpnSense's WAN facing interface and a VIP.

Or, I put two additional routers with ISP's box to get public IP and then another interface with opensense to be put same subnet.

Is this correct?
Can I simply do LAN CARP, and use two seperate WAN connections to each of opnsense box? Then, set up a failover on the WAN side from one Opnsense box to the Other opnsense box's wan, with LAN clients running behind LAN CARP.

Can any one help me with some thoughts and links?

thanks
peng