Flash Drive Encryption questions

I would like to encrypt a flash drive - business use - and have some questions:

1. While I've searched I can find no way to encrypt a Flash Drive via Disk utility? Am I correct? If I'm incorrect, how do I encrypt the flash drive? The only choices I have are Mac OS Extended (Journaled), Mac OS Extended (Case-sensitive, Journaled), ExFAT and MS-DOS (FAT).
2. Is there any up or downside to using an encrypted folder on the Flash Drive rather than encrypting the whole thing via Disk Utility or third party software?
3. I understand I can use encryption software (ex: SandDisk) but what brands are reputable? What should I be looking for?
4. Once encrypted, I'll need to be able to erase the data. I've been fooling around with a Sand Disk that I have and I notice that when in Disk Utility, it shows "Only Volumes" or "All Devices". I also noticed that I can erase both the volume and the device - is there a need to erase both? Am I essentially erasing the encryption software when I erase the volume? And the device is it the "encrypted" partition / folder?
5. Other things you think I should know?

Apologies if I am not using the correct language, please feel free to let me know!

iMac OS 10.13.5

Processor: 2.9 GHz Intel Core i5
Memory: 16 GB 1600 MHz DDR3
1.02 TB available out of 1.11 TB storage