As for the updates, it is recommended that work on a project in one version and don’t move to another version unless there is a good reason. I rule out that the update is the reason for the difference between the viewport and render, but is likely the reason of change in the light intensity.I don’t think we should rush to update to the latest version until we look at the aspects that has affected (You will find that on the Maxon website) and also wait for users’ opinions. The update often has problems, and this is common in various programs. If there is no need, l think it is better to stay on one version and settle with it for a while. I am working on 2024, it is good, and I have not encountered any problems (except for the problems that I caused, of course!) I have also heard many people praising 2025. I hope this is helpful for you.