Hi!
The column count on that view depends on the search bar/container width, as it is calculated from a fixed result width value. The plugin will distribute the results evenly, while trying to maintain the given width.
However, you can define a % width as well. Under the Theme Options -> Isotopic Results panel, you can change the item width, like so: https://i.imgur.com/FtihZim.png
I still recommend using pixel values instead, as if the search bar width changes, the results can get too narrow.
The row count can be set on the same panel, a little bit below: https://i.imgur.com/T1f94kQ.png
