[mr_master]

So I'm planning to encrypt my phones, but I have a few questions beforehand.

1. How much does it affect the phones' performance and boot time?
2. Will I still be able to transfer files over USB (will the files be readable on a PC or other device)?
3. Will files uploaded to cloud storage (I use OneDrive) be readable on other devices?
4. Is a factory reset the only way to decrypt a phone?

[treetopsranch]

You haven't received too many responses to your question because hardly anyone encrypts their phones. They may set a password or pin or finger swipe to unlock the phone.

1. You probably can encrypt folders or files with an app but that shouldn't affect the boot up time.
2. You should be able to send an encrypted file over USB to a PC but only readable if you have the password to decrypt the file.
3. You should be able to upload an encrypted file to any cloud service and readable on other devices if decrypted. I do it all the time.
4. Probably depends on the device but if you could encrypt a phone, it would be decrypted by using the password you used to encrypt it.

[Mooncatt]

You haven't received too many responses to your question because hardly anyone encrypts their phones. They may set a password or pin or finger swipe to unlock the phone.

I thought I read somewhere that nowadays phones are encrypted by default, just not in the way we use to do it. Once you set the PIN or password, it more or less activates the encryption. I'd have to try finding the article again, but it was something to the effect of file level encryption. In either case, my V20 doesn't even have the option to encrypt the phone, only the SD card, and looking into that missing option is what lead me to find out about the change.

To address the OP's questions, you'll be fine. Once you enter your password, pin, or whatever to unlock the phone, you'll never notice the encryption is there. Performance isn't hurt, and files will transfer smoothly. If you tether to a computer with the screen off/locked, it won't be able to see your files until you unlock the phone again.

It will take a few more seconds to boot up the phone, but that is negligible. If your phone has the option to be encrypted, then you should be given the option to decrypt it. At least my last phone did that after I encrypted it.

Just a bit of a side note: The recommended way to prepare a phone to trade in, sell, etc. is to first log out of all accounts, including Google. Then encrypt it if you have that option. Then factory reset. The reset doesn't remove the encryption per se. What it does is throw away the encryption key and writes over data as it resets the OS to stock. That way if any residual data remains on the device (entirely possible), it is still encrypted but not recoverable. Even if you could access it, your password wouldn't work on it because the key is also tied to other things that would've been changed as part of the reset as well.

[mr_master]

Here's a quick update for anyone having the same question:

1. If you own a newer or high-end phone that isn't encrypted, encryption shouldn't affect system performance and you can still use your phone comfortably. Phones released with Marshmallow or newer come encrypted out of the box.
2. If you own an older phone that didn't come encrypted out of the box, how much will encrpytion affect system performance depends on the hardware and how old the device is. For example, encryption didn't affect performance a lot on my old backup phone that came with Lollipop 5.0.1 and was updated to Marshmallow 6.0, but the battery took a hit. This may or may not be because of how old and used the battery was, but the phone discharged noticeably quicker and was warmer than usual. The issue got to the point where I had to decrypt the phone for it to last a day of moderate usage.

[mr_master]

Update #2 : seems like doing a factory reset and enabling encryption again solved all issues on my backup phone I mentioned before.