Enfield Physics has a good selection of OCR B past paper questions that have been devised into topics which is useful. he also shows his workings for most of the questions so they are easier to follow than the mark schemes however there aren't answers for all the questions so you will sometimes have to search them up.
There are also links to old past papers there which is useful
For understanding, ZPhysics is a very useful channel on youtube. While mainly covering OCR A, he tries to make all of the videos applicable to all physics specifications and goes into a good level of detail and clearly explains the concepts.
Seneca is also good for semi-exam question-type questions however only OCR A is on there so you have to be selective about which chapters you do and in some, unfortunately, it doesn't go into much detail.
There is a good set of OCR B flashcards on Anki as well as one Brainscape
While most of them are just learning flash cards, a few do contain some exam questions mixed in.
Hope some of these help.