abrahambelch , 5 hours ago (edited 4 hours ago)

First of all:

You can always copy storage if you’re able to physically access it. The only way to prevent this is to secure the chip in a way it destroys itself if physically tampered with (like some TPM chips).

You should instead opt for a passphrase that is practically impossible to bruteforce on current hardware due to its complexity. Also, try not to disclose the encryption algorithm or software used as this information opens the possibility of exploiting known vulnerabilities.

VeraCrypt for example is able to completely hide its presence on a volume and the only way to know if a device is encrypted with it is trying to decrypt it using VeraCrypt with the correct passphrase.

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Trying to answer your questions:

1. Most modern smartphones encrypt their data by default nowadays. The rest depends on the phone itself. Mostly they just delete the encryption keys from the TPM when formatted so this still enables an authority to copy your storage and bruteforce.
2. No. Encryption does never prevent you from copying the encrypted information. Those are two completely different things.
3. No. You cannot encrypt the SD card with say Bitlocker and use it on a phone afaik.
4. Yes, some Androids allow you to encrypt the SD card from within the storage settings.