Unless you're working at a particularly high profile public company, or some sort of public figure, criminals aren't going to bother. They might give a computer's data maybe a couple minutes to see if there's trivial identity theft opportunity (or porn/movies they can steal for fun, or porn of you they can use for blackmail, etc) but otherwise they're likely to be deterred easily in terms of looking for your data and simply wipe the machine for resale.

Moreover, I suspect your friends are bragging; TrueCrypt/VeraCrypt have been sufficient to keep federal law enforcement out, and iPhone encryption cost the government over a million to get a third party to crack one phone for the San Bernadino lunatics. There may well be better attacks available to intelligence agencies, but if so they're sufficiently secret that they are unwilling to share them with even federal level law enforcement.

You'd need a big flash drive, but yes. The amount of time involved is non-trivial; you wouldn't want to do it daily, but it's perfectly practical.