The practice & revision kit is the most useful, the others less so. You can use the OpenTuition notes and lectures instead of the study text, it’s perfectly possible to get a good mark using these plus a revision kit. The revision kit is needed because it contains a vast amount of questions and it’s question practice that is key to passing ACCA exams.
I don’t know about electronic versions as I use Kaplan materials but I would imagine they do.