Upgrading local test cluster

I created a Single Node install v2.0.8 and then later added more nodes (local Ubuntu servers) to my cluster using… Rancher UI > Edit Cluster > Customize Node Run Command and running the command on some other servers. So now I have a rancher cluster with several nodes. Is it possible to upgrade this cluster?

Do I simply follow the Single Node Upgrade?

Should I be using an HA Install?