My advice is that you choose the players you want to improve and select one or 2 pos trainning according to your plan. Nothing is written in stone. if you focus in lees than 4 player, usually the best is one position trainning. If want more balance, 2 positions.
You may tran some weeks 1, others 2. This takes time, so seize it. You'll make mistakes along the way, it's part of the fun ;)