BigIP 5000 appliance upgrade to 11400 DS

Hi,

We are upgrading our existing BigIP 5000 appliance (In HA) to the new 11400 DS appliance and have a few questions regarding the best approach.

Should we use the Migration assistant tool? It looks like it has not been updated since 2018. We are familar with how to re-key and restore using UCS.
Our On-prem DNS is sync with an Azure F5 ve to perform DNS load balancing/fall back to a maintenance webpage. My question is what is the best way to upgrade/migrate the existing BigIP 5000 appliance to the new 11400 DS?

I was wondering if it is possible to add the 11400 (in HA) guests to the sync group, configure another different DNS listener IP, set up NAT, and update the global DNS side ?