Sometimes one method is more appropriate than another. It depends on a number of factors. There are times when it makes sense to create the “boards” from the path and profile and other times when it makes sense to use the profile like a router bit. Even other times where it makes sense to create a volume representing where the cutter will go and use it to cut away the waste. I did that to create the stopped chamfers on the stretchers of this hayrake table.
If you want to make the frame pieces separate “boards” as they would be in reality, you can pry them out of the frame after you add in the diagonals at the corners. This is a handy way to create the mitered piece with the profiled edge. Basically after you draw the diagonal lines at the corners, you can select the geometry that makes up one “board” and make it a component or group separate from the rest of the geometry. Repeat as needed for the other parts. I used a similar method to separate the leaves from the top on this drop leaf table. I created “cutters” shaped like the rule joint which were intersected with the top and then I made components of the sections.