For a LowRider, there are a huge number of differences between every build.
My 49" gantry has a differenct level of rigidity than Ryans gantry at 24". My Makita router has different amount of weight than @Jonathjon 's spindle. His aluminum struts make it respond differently than my 1/8" hardboard.
Some people are sourcing their own steppers. My printer might be dialed in better than yours and produce stronger parts. Your power supply and screen on your gantry might be heavier than mine.
On top of all of those variables, people like to change things just for the fun of changing them. Adding/removing weight/flexibility all over the place.
That’s not even starting with all the different types of endmills you could be using either.
This is why @vicious1 gives a safe starting point and lets you figure out your own machine limits.
As far as a test file similar to the laser, with the laser test file, if your speeds are too high, you just won’t get a cut or engraving. If you run a test through all different feeds and speeds like that with a LowRider, and you max out at the very low end, the high end could be disastrous.
I think part of the difference is that with the laser, those files are meant to see how the material responds to the machine/settings, where in the LowRider case, you want to know how the machine responds to the material/settings.
When the thing in motion is the thing under test, you want to be a bit more careful and ease into the limits, stop, and pull back a little. The laser test can go well beyond the limits of it being useful on the material and nothing breaks.