Hi, Micheal!
I just happened to run across your question and noticed it had not been answered.
I’m not on the Apple platforms, so I’m not familiar with exactly what recording apps are native to those, but you should have native apps that allow you to make voice recordings. You can pair a quality Bluetooth microphone to your device if you want better sound with less background noise. I think mp3 is still the most common audio file format and it seems to still be supported by most audio playback apps. The mp3 format cannot be password protected, but you could add them to a password protected zip file or upload them to a password protected cloud folder.
You should be able to create a shared, password protected folder in Apple iCloud, but you would only be able to share it with other users who have iCloud accounts. It may be possible for non-Apple users to create an Apple ID that allows them to access. There are other cloud services that could be used, such as Dropbox, but they may require you to have a subscription to password protect shared folders. I personally am using Microsoft OneDrive which allows me to create password protect folders that I can share with anyone.
I hope this information is helpful.