As you know, there aren't many options in the Numbers prefs.
Other columns shouldn't be moving at all when I widen or narrow one column. Only one column should move. This happens regardless of how much screen space there is. I have plenty. It's such a dumb problem. Appleworks never had this problem. That was a long time ago.
If I select one column by clicking on the column letter at the top of the page I can either drag the column to the width I desire or specify the individual column width under Row & Column size under Table
ONLY THE WIDTH OF THAT ONE COLUMN CHANGES.
If no column is selected and I set a column width under Row & Column size under Table
THE WIDTH OF ALL COLUMNS CHANGE.
The same is true of row height as well.