You can import directly your photos from any cloud service that is compatible with the Files app: iCloud, Dropbox, Google Drive, Box, One Drive. To do so, you need to select:
Tap + button
Tap Import from Files
Select the cloud service you want
Select your Photo
You can then edit your photos as usual. Note that you can also directly export back to this cloud service.
Also, on iOS, make sure your Dropbox, Google Drive or iCloud apps are connected in the Files app.
Note that the export order will be different by using the Files import option. It is a current limitation on iOS that we don't handle.