I have the same issue. A workaround until Airtable creates the ability to set column width in page designer:
Name your columns something like “ColumnName …” where each column has the name you want displayed then a space then a series of repeating characters (either dots, dashes or underscores work well here). I assume the software see this as one big ‘word’ and adjusts the column widths to try an fit this big word. So each of my columns has a name, space, then a series of these repeating characters. By playing with the number of repeating characters in each heading you can get fairly good control of the column widths. Of course your headings will then have this second row below them with these special characters, but that’s not a huge deal for my application at least.
