I am displaying over 60 options as checkboxes in the grid. There are just two columns - name, and checkbox. It makes it too long and narrow.
I could make two columns of the options. So, 4 gridcolumns - name, chkbox, name, chkbox. This would only work, if I could thicken the central grid line that separates the two.
Try using grid.OnGetCellClass that allows you to specify a different CSS class per cell.
For just the cells between the 2 columns, you could set a CSS class for a thick left (or right) border.
I can only think there is some conflicting Bootstrap class.
I'm not sure what you mean with "do I use element set to span" in this context?
I have not tried out all Bootstrap classes in such scenario myself. I will need to check first myself.