I don’t know if I missed something on the way but I had done easier (assuming that Paul will use an only one Choice component).
The InLine List supports a multiple relation as a data source so, let’s use it!!
1- Create a USC to hold the category selected by user
2- Create a multiple relation using the above USC with Categories table’s Category column. Let’s name it “rel_Cat”
3- Put your InLine List and set its data source (Sheet Source) to work with “rel_Cat” relation
4- Enjoy the solution
But if @paul_Okoduwa is going to use 2+ choices later to get a dynamic filter, the steps showed by Darren or Robert in his video are good choices although we have a plan B as well.