hi @FCNVillangca both the enterprise plan and on-demand are paid.
The difference is that the amount covered in the plan is fixed and on-demand uses as much as you need. Cursor uses first the amount on the plan and only once used up, it switches to on-demand. There is no manual switch.
For models, see the docs page that shows smaller models that are cheaper and may be enough for simpler tasks, therefore save money.
Check following page on tips how to use Cursor more efficiently: