(Now I want to give a heads up in saying I work more traditionally with pen and paper so I apologise if I make too many references to... Well pen and paper.)
I think the effectiveness of any technique is primarily based on the individual but it is also important to consider the purpose, time frame, energy, and knowledge you plan to have for these tools.
For people who earn major benefits from working with spaced repitition, prompts and active recall with short amounts of text, flashcard tools like Anki can be extremely effective and generally will work with everyone and is a safe option.
However this may not be the most effective if you find more worth in:
blurbing which uses active recall and works well with knowledge stored in their long term memory (which is why it is used to assess what topics has escaped your memory over a period of time) ,
summarising which transforms new knowledge into your own words (this is most effective after reading through a section in your topic to consolidate fresh knowledge that is still strong in your short term memory) ,
attempting exam questions on the specific topic you are currently studying. To focus your practice, avoid full past papers (however you can take questions relevent to your topic from the paper). You should use this as a consolidation tool to facilitate embeding what you have just learned into long term memory which is then applicable to answering your exams and scoring those sweet, high grades (which actually reduces the need for flashcards)
or just writing out all you have learned from the section you were reading from. This is similar to blurbing however it is done after the reading and retrieving knowledge from short term memory rather then before deciding on what to read and retrieving knowledge from long term memory. You can use this to go over any key information or additional points you missed on your first round and ensure it is written on your second round (or just simply mark in green pen the missed points so they stand out enough.)
Be careful! What you are trying to do is embed as much relevent information (subject specific knowledge) into long term memory that is easily accessed. It doesn't matter how many summaries or notes you have written if none of it sticks into the ol' noggin.
(Understanding design theory and having easy to read notes can vastly improve your results as you can steal a quick glance easily without having to spend time and energy trying to make out what you wrote - remember conserving energy and reducing the time spent is just as important as putting in effort and revising to maximise what you get out of studying! Using a bright colour that stands out from the rest of your writing can draw attention to keywords relevent to scoring marks in exams or help remember statistics. )
Like I mentioned, the techniques you choose to employ depend on: how much time and energy you want to spend with these, whether this is for last minute exam prep or starting early revision, and what knowledge you are hoping to improve (if what you need is an essay-styled answer to a question, essay plans are much better and would be too large for flashcards!). Conversely, because of the little time spent on flashcards and ease of transport (Anki being digital), they can be used as last minute revision before an exam or just a small activity during a commute - which you will do often.
However realise what is most important for these grades are your ability to work well under stressed conditions, quickly and swiftly, easily retrieve all necessary memorised knowledge, and fitness during the exam (imagine being exhausted from overwork, cramming, or all-nighters on your test!).
So all in all, what you need is to find what works for you to help you achieve the best results with the littlest effort: this means managing your energy well, allowing knowledge to consolidate and form in long term memory, filling knowledge gaps, and having experience with the exam questions to know what examiners are looking out for. Thank you.