Design question - Multiple (four) ISP's - Two are BGP capable

[fcb]

So the title about says it all.... We have an HA cluster (Active-Passive) with two 500's and we have FOUR ISP's that are connected into these units. One is broadband (Xfinity), One is a 1 Gb Fiber, and the other two are from one provider (Segra) with two 1Gb "legs" coming into our main facility. This provider (Segra) also provides us with a 1G connection at our DR. They can utilize BGP and dynamically move our WAN IP's to the DR location in the event that both "legs" are down at our corporate center or main campus... I love the thoughts of this in the unlikely event that our main site is down (fire, natural disaster, pandemic outbreak, etc), everything auto-magically rolls to the DR site where the exact same VIP's are ready and waiting to accept the inbound connections so we don't have to scramble around and change the A records at our registrar and everything will just work.. I do want to utilize the SDWAN capabilities and understand the SDWAN rules, SLA's, etc. but it's a little foggy on how the two will work together. I've seen several design guides around this topology/setup but I see some potential pitfalls in some of these and am wondering is anyone has implemented a solution to cover my use case.

I get that this is a very high level overview that  have provided but am looking for a high level solution/suggestion.