You cannot downgrade from version 2.x to version 1.x automatically (without manually re-importing datasets with recovery APIs)

Upgrading from 1.x to 2.x is done for you automatically, with data migration. See release notes for version 2.0.0

Since ConfiForms app version 2.0 we will publish release notes here

Version 2.0.0

ConfiForms now has a new storage layer, with much faster edit and delete operations. And with faster and less memory consuming search / filtering operations.
There are no limits on the dataset size per form. And the size of the record is limited by the number of characters your database can hold in a CLOB type field (ConfiForms limits are 2,147,483,647 bytes)
Data migration is done for your automatically when you access the form for the first time. This could take some time for the first load, depending your your dataset size
There are methods to help you to understand how you data looks like and force the migration via migration APIs if you want to do so (accessible only to Confluence system administrators)
Storage analysis
[YOUR_CONFLUENCE_SERVER_URL]/ajax/confiforms/rest/storage-analysis?spaceKey=
Auto-migration
[YOUR_CONFLUENCE_SERVER_URL]/ajax/confiforms/rest/auto-migration?spaceKey=
Your tables will look different and use the cleaner styles as provided by AUI - https://docs.atlassian.com/aui/7.8.0/docs/tables.html
Your forms look cleaner as well, and also follow the guidelines and styles from AUI
ConfiForms is DC ready (approval is in progress)