Initialization of the tournament consists of cleaning up in entirety. It is completely returned to the begin status. The participants remain saved, the draw is renewed to the original state, but all results, plannings, etc. are deleted.
You can select a certain age category of the tournament to clean-up. This has no consequence for any other possible available categories.
After the clean-up, you do not have to run the category wizard. You only have to start planning again.