Multi WAN configuration

[Jamerson]

Dear All,
is it possible to configure Multi WAN over the VPN ? would I lock my self down?
we have TWO WAN,  WAN1 and WAN2.
we want to use WAN1 as our main connection, whenever WAN1 goes down we want the pfsense to move to WAN2.
do I have to create one TIER 1 for WAN1 and WAN2 and TIER2 for WAN2 and WAN1 and both high latency on the trigger level ?

thank you