With regards to ending the welfare state and having an open border, the order in which those two things happen is crucial to the outcome.
End the welfare state first, and an open border (with some nominal checks for security purposes) might be feasible. Opening the borders first - as has happened - invites a globe full of benefit-seekers to come and suck the life out of the country.
Of course. But because all countries/cultures are not equal, and we are in the unenviable position of having a prime example to our south, there will always be “economic refugees”. Our country would continue to be flooded with those that would work for frijoles.
In the end the libertarian platform is little more than theory, like communism, that would never work in the real world.