XMind Pro has more business features than XMind Plus and also a higher price. XMind Pro and XMind Plus are both life-time packages. But we don't support upgrading to XMind Pro from XMind Plus at present. The contrary downgrade is not available either. So we recommend you understand your requirements and compare these two packages clearly before making a decision.
BTW, XMind Pro Subscription charges yearly subscription fee. It's a different business mode. So of course, you can not change to others either.