From what I understand, updating in-place is the most common and default way to update Viya 4. You can find details of the steps in the Viya documentation. This link is a good starting point.
I'm told updating Viya is a lot quicker and smoother than SAS 9. However I still wouldn't recommend doing it if you are a Viya novice and have not had prior SAS installation training and experience. SAS's architecture is so complex these days that I prefer to leave installation to specialists. In your particular use case you need to be familiar not only with Viya, but also with AWS and Kubernetes.