best study pattern

2 only if you need the change. Sometimes I get tired of one, at which point switching does help. But you should average one at a time.

Too many subjects spoil the broth

Go one after another.

Good enough to keep your boredom level minimum

Only two if you’re only got two weeks to the exam and still haven’t finished the syllabus!!

If by subjects you mean Economics, FRA etc. then stick to one. I tried to do more than 1 chapter a day in order to get through the material enough times.