Hi Saki,
I'm using RowActions for the first time, so this may be something I missed.
I have a working grid. When I add an action icon, the widths of the columns change row by row based on their content and don't align with the header row.
The action icon is the + symbol in the rightmost column. When I remove the plugin all the widths are as specified in the width properties.
I'm using extjs version 3.2. The grid is an editor grid panel. I haven't shown the leftmost columns due to sensitive data.