Yes, after 14-day trial, you are allowed to select the plan which suits your need. During trial period, you are not allowed to switch the plan.
You can also upgrade to the higher plan once you have subscribed to any of the plan.
Downgrading to a lower plan, however, is not permitted during the subscription period. You can choose to downgrade your plan at the renewal of your subscription. Please let us know in at least 7 days in advance to avoid automatic collection of payment at the start of your next subscription duration.