[yigitdemirag]

For books, PDFs : Zotero (if book/pdf requires to be sync have a copy at iCloud) - Because I usually need to cite these things.

For notes: First condense the thought and put it nicely to Dynalist - Because it is all easily searchable, linked and think-then-write tree-structure. - Mobile app is a must to capture ideas, thoughts on mobile.

For todo: Things/Todoist etc. would work. - Because you need deadlines, reminders.