There is a freeware software that can post-process g-code and handle the odd-shaped beam spots correctly.
He was cutting out gears (circles with teeth) and a circle will come out slightly oval due to a rectangle (really more like an oval) tracing the path in a circle.

If I want to cut out a rectangle "perfectly", I can rotate it 45° so the kerf will always be the same. There are some lenses and laser modules that also compensate the shape to produce a circular spot, but that comes with the cost of upgrading.
Anyway, I can "fix" most geometric shapes if I need to. More organic free-form shapes are a bit more difficult to fully correct, but then again it's only a couple of thousandths of an inch.

Cutting veneer doesn't take much power, 5 watts will do, you just go a little slower.
I can cut 1/4" plywood and masonite without trouble (10 watt), but it takes more passes or much slower speed (= more time).
True cutters are CO2, blast through most anything and their prices keep coming down, but still north of $1k

Smaller diode lasers with smaller work areas (< 1 sq.ft.) are getting really cheap (low hundreds)

It's a neat tool! Nothing yet that I couldn't do with other methods, but for burning in lettering or cutting random shapes is a lot easier to do quickly and accurately without dedicating hours of training to do it like the Masters do.