Linux Boot/Hardware Question: Flash Drive Key?

Hello all, I'm trying to switch to Linux (not sure which distro yet) and I've heard I can run Linux from a flash drive without installing it on my system. I'd like to make it so all my non-OS/driver files save to my hard drives, but without my flash drive the system is just an encrypted paper weight. Is this possible to do and if so how?

Also on a hardware related note, would it be better (safer/faster/expletiver) to do this from a USB 3.0 flash drive or eSATAp with an SSD?

Thanks for any help and sorry if this is a stupid question, I'm by no means a PC expert, that's why I'm here asking you guys.

Not sure what you mean. But yeah you can boot from usb easily. Just download the ISO of your distro of choice and restore the image on a USB flash. Then you just restart and have the BIOS to boot from the usb and you are done...
Mind you will lose the any data on the usb flash.

I also i think that the USB flash will be more convenient.

Thanks for the quick reply and sorry, my wording may have been poor on that one, I mean make it so there is no OS at all on the system, but keep files on it in some way so the system as a whole only works with the Linux USB plugged into the front. Making the flash drive a kinda key to the system if you will?

I have used LinuxLive to make flash drives for friends but never myself, will that work for a bootable or only for installations?

Never tried that before to be honest but I do not have a reason why it should not. Free NAS can do that at least, so i guess a live Linux on a usb should be ok. . I would google around a bit though just to be sure.

And yes a live installation on the usb will do just that.

I guess I will do some research while I get a distro downloaded and try, I appreciate the help and hopefully I'll be back soon with it working as intended.

I would recommend ElementaryOS because of its clear and simplistic feel. Looks like Mac OSX, if that interests you.

edit: Although I have had some problems booting it from a usb, smh.

USB 3.0 would be faster, not sure if it would be safer though.