For Word study in particular from what I understand, each study vector selected adds an additional review for each word being studied. This can greatly inflate the number of revisions that stack up each day just because someone wishes to study multiple different facets of a word.
For example, I am greatly enjoying the PRO Listening Questions however using two of the three of the vectors for this has doubled my reviews when using in addition to just two other vectors. This becomes unmanageable and overwhelming.
Instead of creating a new review for each vector can instead there be an option for when a world comes up for review, it randomises/cycles the chosen vectors. Then a broad variety of study can be achieved without being overwhelmed.
When adding new vectors you may want to consider checking this option: Prevent newly added vectors from flooding this schedule with reviews
"Adding new study vectors can greatly increase the number of reviews you have available. Leave this checked to make sure the reviews are spread out over the coming days/weeks."
Also you may want to consider changing the Study style (in the Advanced Schedule Settings) from: Slow and thorough (The term will gain a mastery level each time you answer all of the study vectors.), to Quick and Simple (The term will gain a mastery level each time you answer any of the study vectors.)
