In my state in the US, a person calling themselves an "engineer" has to be licensed.
However, this is only for someone offering engineering services directly to the public. If you do engineering work for an employer, then you enjoy an "industrial exemption." At my workplace, we design stuff, then the design is checked by a third party (such as a regulatory approval outfit), which provides a technical report signed by a licensed engineer.
When people start their own side businesses, they call themselves "technology," "research," and so forth.
From what I've observed, remarkably few engineers do any engineering, such as determining appropriate strengths of structures, etc. Most product design work seems to be done by trial and error.