You should try increasing the container width of the box, so the input can get wider: https://i.imgur.com/e859fpr.png
So it can get to the edge of the screen. Decreasing the padding on that could also help.
For the plugin you can set a fixed width (either pixes, %, vw units) here too: https://i.imgur.com/isa6jFX.png
By default the search input occupies 100% width of the container, but sometimes it might be conveniet to set a fixed width.
