primary sources for phys and path?

I used BRS for both physio and path as my primary. Many chapters in those 'review books' as you call them are very dense and if you literally read (not skim) the chapters on a given subject, it very well will take longer than an hour to get through and do the chapter review questions. The review books were designed for step I studying for their given subjects. To try and read "primary" texts to study everything needed for the boards would take more time than you have.

Robbins is VERY dense and detailed and IMHO not broad enough for Step I review. Using that would be very ambitious (I dare say too ambitious) and probably burn you out above and beyond how burned out everyone gets studying for boards. If I didn't understand something, I first would look in Step-Up or FA to see if there were "simpler" explanations in those books. otherwise, I would ask someone or look it up on the internet (for physio) or in Robbins or Harrisons for path. Usually, I didn't need to look anything up. You've learned it all once, what you want to do now is remember it and apply it to a situation.

Some people I know would do the relevant Q-bank to their day of studying. i.e. if they studied GI phys that day, they did GI physio questions on Q-bank that night.