SNAT for two ISP routes on Fortigate

hello
We are trying to obtain two ISP lines by adding a new ISP line to the existing single ISP line configuration.
I don't know yet whether these two will be configured as active-active or active-standby.
SNAT is required for both lines, and in the case of Active-Active, two IP pools will be applied to the policy to enable sequential NAT processing.
However, when operating as active-standby, I do not know how to switch the SNAT IP in the firewall when switching lines.
If you have experience or know anything about this situation, please help.