Prices are in US dollars.

Feature wise they're generally the same. The difference is that if your organization need more than 1 user to access the account, you would need to use a Plus plan to have more than 1 user.

Subscription charges are prepaid so you will be charged the moment you upgrade. After that, you will be charged at the start of next billing cycle. For example, if you subscribe to monthly plan, your next charge will be 1 month from today.

You can cancel subscription by yourself in self-serve manner. Just go to billing page to cancel subscription. After cancellation, you won't be charged after further. Since RenderKu works on prepayment, you will still have access to your current plan until end of billing cycle.