What is the best way to get an idea of what a carve will look like before it is actually carved?
It depends on what design software you are using.
I run vcarve pro and it has a preview window and ugs has a visualization window that tracks machine movement in near real time.
Camotics will show you the end result and the toolpaths as it is cut, not is real time though.
Another vote for Camotics. I run every potential cut through the software and has saved me countless number of times. It’s free, Open-source and looks to be available for all platforms. My entire tool chain is OS and this is a main part of my arsenal.