I think free movement of people doesn’t imply Schengen Zone style borders - I thought this was mostly an economic lever that people can move and work in another country by default, not a human right where a country cannot exclude chosen people (known criminals, etc) and track all crossings. I think of it as another country giving me a visa is opt-out for that country, not opt-in.

The CE rules are relatively sane and followed commonly right? At least I see a lot of CE-stamped goods in Australia… so I always assumed that was the case.

CE is a tool against protectionism. If a thing is CE stamped, you must allow it to be sold (if you're a member).

All that Schengen does is dismantle border checkpoints. As a German, I can freely move to any EU country for any purpose - transit, tourism and work - no matter if, say, I were a convict or whatever.

There are expulsions and entry bans even under Schengen, but these are incredibly rare things to happen as the freedom of movement is considered to be a cornerstone of EU values.