The problem is EASA updated to a new central question bank last year (ECQB2020) and those apps are still not completely up to date with the new questions. It will take some time until they catch up since they are dependant on students currently undertaking the exams provide feedback.
From what I hear you can have anything like 10% to 70% of your exams coming from those apps at the moment whereas in the old ECQB it used to be easily 70% or more, so it's a big bet relying solely on it for studying.
Your airline experience will definitely help with many subjects, but I would recommend buying some theory books to review some subjects and use the apps in parallel to practice (and read the explanations). I heard Padpilot ebooks are quite straightforward to read and updated with the latest learning objectives.