[uoaei]

Is there an up-to-date source on which countries do what kinds of scanning/copying?

Is it the case that device-level encryption successfully prevents access to the contents, or is that a layer I should refuse to trust?

[renzo88]

Depending on country laws, refusing to reveal keys or even device-level encryption itself may be illegal/cause you to be detained.

The best thing you can do is bring a wiped device through, and assume that it and its data can be seized at any time. Also treat any device as disposable - once seized, it should not be trusted.