Tactics creator only and not tweak?

I thought there was a thread about this already if there is I apologise in advance. I am currently playing a game all over the world going from league to league. I want to start a game as a big club I am thinking Man United or Spurs. I was just wondering if people only use the tactics creator roles and do not tweak any of the instructions. I was thinking as Man United that there are quite a few options for the midfield and down the wings and it would be easier to just select a role for Giggs and Nani when they are on the left rather than tweaking the tactics each time. Does the tactics creator alone allow successful tactics or is tweaking needed?