For つばさ文庫, start with one novel and see how things go. After all they are aimed for kids and might be a bit dry… I strongly recommend going on Bookwalker or any digital store and trying out the sample before spending any money on them.
For つばさ文庫, initially I read ずっと前から好きでした. Its part of a project by HoneyWorks ( 告白実行委員会〜恋愛シリーズ ) . There is an anime (“Our love has always been 10 centimeters apart”) , two movies and two books . I saw part of the anime, which is lightly connected and thought why not try that book. I probably looked up most words and unknown kanji.
For Mirai (未来のミライ) and Summer Wars. I tried to look up only the repeating unknown words, not everything. That way at least its easier to get invested into the story by not stopping all the time hehe…. After I watched the movie (with English subs). Just to see if I understood things correctly.
Sometimes, I don’t look up any words and just try to understand from context and not worry about it. For 2/3 light novels, I actually re-read them a few months later as I found it helpful to better understand things.
Btw, there is also Bunpro’s Reading practice section!
For digital flashcards…. This may sound strange: “Do you really need them? What do you want to gain from digital flashcards”. It seems like your study methodology is already good enough… Probably getting something like Kanzen Master JLPT N3 for vocab / kanji can work just as well….
Bunpro’s vocab decks are already in beta, hopefully they will be released officially soon 