TPR isn't that much different than the AAMCs in my opinion.
bio might be slightly harder but everything else is on par. i stopped taking the TPR after the 3rd one (23, 27, 30). once i hit 30 i went with the AAMCs [30, 32] ( i was getting behind on the tpr homework/tests ). I got a 32 on the real thing.
i would definitely suggest taking as many TPR and AAMC tests as you can. i only took 5 because i was getting burned out. however, in hindsight, the more practice the better. i definitely could have used the extra practice. even if you can't do all 3 sections in one sitting, go through one section at a time. that whole hour + time it takes to correct the section is a good practice session.