In my opinion it would be important to have the chance of make this setting visually: by switching to text mode it becomes much more difficult to modify other settings, and this is bad just for having to set the width of the column. I think there are many scenarios in which columns could have widths set permanently, and we would like to avoid users continuously resize columns, especially when losing their settings by clearing cookies/local storage. or when resetting users.
To make matters even worse, the handle that allows to adjust/resize the column width is too small to be usable without pain, as user @MatthewMa2 properly explained in his idea. I agree that those handles should be at least twice the size to avoid people be frustrated misusing it, for example by clicking on the column heading and changing the order of the list instead of adjusting the column width.