Since you are working with the edit forms, I would suggest you to remove all the datacards and add them again based on the SQL Data Source. This would be a better approach as this will avoids all the discrepancy in the back-end processing of the form. We donot have much control over the datacards and the main issue will arise if the Update property doesnot refer to the required value.
Hope this Helps!
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In general, I think it's safe to modify the DataSource property of a form without PowerApps reformatting the content.
What I would recommend you do is to backup your app onto your local computer by going to File > Save As (This Computer). That way, if the form designer messes up your work, you can revert back to a copy that's correct.
Do you want to repoint the Edit form which connects to your Google sheet table to your SQL Table?
Actually, when you re-point the data source connects to your Edit form, it would show up a prompt as below:
On your side, if click "Replace my data cards" option, then all data cards in your previous Edit form would be replaced with columns from your SQL Table.
If you click "No Thanks" option, the previous data cards from your Google sheets table would be invalid. You need to remove all data cards from your Edit form, then enable the corresponding field data cards from your SQL Table.
Currently, within PowerApps, I afraid that there is no way to get rid of reformatting the Edit form when you repoint your Edit form to another different data source.