I was in contact with the library creator and he does want to improve the responsiveness of the pagination menu, so hopefully we will see improvements in the coming library update!
If you want to add custom css to the table, you could use the inspect element function inside your browser to make changes to the css on the page and see the result in real time.
I could look into if I can maybe add the oprij to let you specify the column and row borders separately. I think I looked into this in the past and was running into the issue that both borders shared the same class, but I will look again to see if this is possible now
The table should not re-render after a workflow action. The table does re-render every time the data is changed (or other features of the element). Does your workflow action cause a change of data? If so you could maybe look into preventing this to keep the table from re-rendering
Totally understand your situation here! You could append the columns via workflows to have the ability to easily reorder the workflow action when a change need to be made. Would that be of any help in your situation?