[Paid Software Announcement and Discussion] LastQuestion:
I can't speak to encryption, but I know a bit about how some call recording applications handle storing and accessing the recorded files and how to transfer that information.

I have been using Automatic Call Recorder by Appliqato. Long story short. I had to downgrade app versions to keep a feature I needed. After downgrading the application could no longer list (let alone playback) any of my previously recorded calls.

The really short version of how to get the information without root is to use the ADB interface to do an ADB [backup -apk -shared -all] command, unpack the .ab file to .tar via command line, open the .tar with 7zip or unpack via tar command line, then grab the package for the call recording application (basically the folder for it) or transfer it via command line, then find the database file the application uses, open it in a database viewer, and then transfer the information grid by grid to the other app's database file (similarly pulled via ADB backup). The database files were not transferable between versions in my experience (different columns were present; probably other differences too).

After getting all the information transferred, get the .db file (or other file type, if the app uses a different way to store this data) transferred to the new applications package folder. Then pack it up into a .tar, and pack that tar into an .ab, then use adb restore (just pointing out an obvious here - one should only pack up the package for the app you want to change - the rest of the application data pulled via adb backup shouldn't be present at all.).

Doing this between versions wasn't easy as the db viewer didn't much like pasting in fields from the other .db file. Doing a transfer between different applications might be quite tedious, but I expect it's possible, so long as the application is storing information in a database file.

With root, one wouldn't need to use ADB backup/restore. But process is still involved editing and transferring database files.

I won't know more unless I find I cannot get ACR to work the way I need to on my new phone. For example, if I end up needing to root for 100% reliable call recording, then I'll have to transfer things to an application like Skvalex's Call Recorder.

Also, doing that type of transition, might require converting all of the audio files into a format the application knows how to play. For example, some call recorders do not offer .aac recording, so it's unlikely they'd work well playing back an .aac file. So all .aac files would likely need converting, then editing the field in the database file noting storage location that the file type is <file name>.mp3 instead of <file name>.aac.

It's issues like that which keep me from dropping ACR. Just want that to be clear. Because what Skvalex is doing is really great work. It's a solution where otherwise there is nothing. And no call recording app is perfect in my experience.

For example:

ACR's audio capture is really high-quality. Especially in .aac. But ACR has no root option. And on my S5 it is call recording is unreliable for reasons unknown. The developer (Appliqato) offers basically no support or documentation which would help one troubleshoot.

Skvalex's Call Recorder capture quality with a similarly lossy format (mp3) isn't all that good. But if you record in .wav at 44.1-48khz then convert to .mp3 it improves; yet that's a lot of extra work if recording every call. However, Skvalex offers a version of the app which accesses Call Logs (so you can see numbers/names of incoming or outgoing calls not in contacts), he actively supports development, he seems to have pretty much pioneered including a working root method for recording calls, and because of that, it's most likely that despite the lower capture quality of audio the application will provide more reliable call recording, with or without root.

There's a lot of guides out there, which will need to be read and pieced together to get a database transfer done between app versions or between different recording applications. And even then, it won't be simple or noob friendly. Eventually I'll try to make a guide to this which consolidates things so that it's not too hard. It's a very niche problem. I'm still in the middle of my own issues, so I don't know when I'd be able to do that guide. Until then...good hunting.