Moving files from an internal HD to an external HD

I bought an external Thunderbolt drive so I can transfer the content of my Late-2013 iMac to it. I was going to use Carbon Copy Cloner but since I use FileVault and have 3 accounts, I'm assuming this won't work.

Instead, I'm planning to download Mojave and install it on the Thunderbolt drive, while activating FileVault and then using Migration Assistant (MA) to transfer everything.

My questions are:

• If I have 3 accounts on the Mac, should I create 3 accounts on the external drive or MA will do this automatically?
• When booted from the external drive, will I be able to use MA (since the internal drive has FileVault and passwords for accounts)?