Boundary hedge / lawn edge

Best with the cheap Chinese granite that everyone built everywhere on their property 10 years ago.

No idea what you mean. We have shell limestone granite. Looks great and solves the problem of lawn growing into flower beds. In addition, our lawn mower robot can cut edges cleanly.

just let it grow and mow as far as you can, why does it always have to look "neat" and straight, nature is not straight and tidy.... stick to your wife's wish
when the hedge gets denser, little to nothing will grow underneath anyway... mulch is fine, it retains moisture better.