While technically true that overwriting files makes recovery more difficult, nothing is impossible. I'm trying to follow your post. You had files on your device before you encrypted it. You then have or are planning to encrypt the device, which is it? And you would like to know if files before encryption are recoverable, after you recorded some videos with the intent to overwrite the previous files. Is this correct?
First memory doesn't work that way. Imagine a football field. Now imagine you want to save a picture of a football. The image is rather small, but imagine taking 8 footballs and spreading them out between the 30 yard line and the 32 yard line. To delete the photo you take away 2 of the footballs, and your device wont see it anymore. The bulk of it is still there but your memory sees these as fair game for any saves that come up, not necessarily for the next thing it saves. Memory isn't neat little packets that are arranged all in a row, starting from zero and moving to 100, even though that's what it looks like when you view files. It is also not evenly distributed from beginning to end. Some thing may save on the 40 yard line this time and the next thing on opponents 2 yard line. Ever see an image load the top portion and slowly fill in the bottom? So if you record a video you may hit one or two more footballs but the other 4 are still out there and those may be the pieces that create the top, bottom, left or right side of the image. This randomness is why wipe software overwrites the entire drive with 1s and 0s and for a really good wipe does this multiple times. The more times something is overwritten the harder and more impossible it becomes to recover but randomly recording video or adding files does not guarantee you are overwriting anything. FYI if law enforcement gets access to a drive, even one that has been overwritten two or three times can be recovered. Hopefully you don't have legal issues that would make such measures necessary. Having said that, given that you've taken to posting on a public forum about this, my guess is that you don't have any data worth the trouble to protect this extreme and unless you feel that your device is vulnerable to being accessed for hours without your presence you're overacting to something that shouldn't be more than a blip on your radar. Android is fairly secure. Factory resetting the device once or twice is about the most extreme thing recommended when selling a device, a point in time when someone has no control over the device, so it's fairly safe to say that your data will be OK if you deleted it, factory reset the device and intend to encrypt it from now on. If you have any other questions or concerns please register an account and reply to this thread. This link will help you do this...
https://forums.androidcentral.com/ask-question/409154-join-android-central-community-new-post.html