> Would to prefer underregulating it?

No

> How would you find the exact amount of correct regulation?

Difficult problem. The issue right now is that nobody wants to be seen to remove a regulation from a nuclear. One of the biggest things is that ALARA/LNT needs to go away. It is not useful, and it is not based on good modern science

Creating new assessments based on modern research would be good and there is already a ton of evidence around that could be foundational for making real science based changes

Changes to bring regulation in line with actual risk would be a good start: https://m.youtube.com/watch?v=gzdLdNRaPKc