Cambridge is better to use throughout your year as the main t/b because it has questions starting off easy then getting harder so you have the concepts down pat before doing harder questions. Sometimes fitzy has hard questions in the beginning and I don't really like using it for longer periods of time (idk why) lol but Cambridge also is easier to work with (colour and properly structured).
Also, Cambridge has better explanations and examples which run you through the working unlike Fitzpatrick which does not have many explanations but instead just has loads of examples.
When used in conjunction with Cambridge, Fitzy will help I guess but tbh Cambridge should do the job along with plenty of past papers and you'll be on your way to a b6/state rank/whatever you're aiming for