If you want to try UniEC before committing to an active monthly plan, then you can sign up for a free 14-day trial. Your free trial begins when you first sign up, not when you start working on your store. You won't lose any of the work you complete on your store during your free trial when you choose a paid plan. If you choose a paid plan during your free trial, then you won't be charged any subscription fees until the end of your free trial period.
You can set up your store during the free trial, but you need to choose a monthly plan before you start selling your products or services. If you don't select a monthly plan at the end of your free trial, then your store will be paused and you will not be able to continue working on it until you choose a paid plan. If you don't choose a pricing plan during your free trial, then you don't need to take any action to cancel your UniEC account.