Suggestion about redundant conecction.

Hi, I'm a little confuse about how apply redundant connection and failover to internet and VPN tunnels with fortigate. We have a Fortigate 80E 5.6.4 in one side and a Fortigate 50E 5.6.3 on the other side. So, I thought that using SDWAN we can get what we want; when a link goes down switch to use the other link and everything keeps working, this in reference to the tunnels VPN. Reading about this I found the "fortigate-ipsec-vpn-50.pdf" document and read the topic "Redundant VPN configurations" where they explain how is the configuration using tunnels VPN but they don't mention anything about SDWAN. At this point I assume that exist various ways to configure it but I don't know which is the best way? any suggest? What about with the internet services, with a basic failover using ECMP its enought?

Thanks in advance for help.

Greetings