transferring all photos from one account to another

I'm afraid there's no easy way to do this. The Lightroom Downloader isn't really designed for this purpose, though I'm surprised that your edits weren't preserved.....unless you only have Jpegs in the cloud? The Downloader is meant to download all Raw files with edits in an XMP sidecar file, so as long as you keep the XMP sidecar in the same sub-folder as it's companion Raw file, then those edits should be read from the XMP file on subsequent import back into the new account. Jpegs, however, are treated differently (or they did the last time I tested the Downloader), and I found that the orginal Jpeg is downloaded (so no edits as Lightroom is a 'non-destructive' editor), but a companion "exported" jpeg is included (which are likely the extra files you mentioned) which have the edits baked in.

There is another method which can be used, which avoids the download/upload scenario and preserves all edits, but it still doesn't (easily) deal with the album structure. Basically, the steps would be:

1. Log on to your new account, start the Lightroom desktop app and create an empty album which you set to share with the email address of the old account. Share settings must be set to "Can Contribute" and include all the metadata options as well.

2. Close Lightroom, then log on to your old account, having accepted the invitation from the new account, start Lightroom again and in the Shared Albums>Shared With You section you should find the album that you created in step 1.

3. Now you can click on All Photos and select ALL the images in the library, then add them to that shared album.

4. Wait until done (syncing has stopped), then close Lightroom and log out and log back in to the new account.

5. When you start Lightroom again under the new account you should see all the images from the old account, but all in that one album.

To preserve the album structure you could do the above process but doing one album at a time. Would be very very tedious if you have lots of albums.

A variation on that would be to apply an album-specific keyword to all the images in the old account (before you start this transfer process), then when the transfer is complete you can rebuild the album structure by filtering on the album-specific keywords and use those to manually recreate the album sytucture. Also tedious, but maybe a little less tedious than transferring one album at a time.