Manual only: the planner reads nothing from your Old School RuneScape account. Your bankroll, reserved gp, skills, quests and owned gear are all numbers you type in. They stay in this browser, and you can export or import them as a file.
Affordable now means the
operating float for your plan window (input cost per hour over the window, plus extra when a buy limit makes you stock up ahead) fits inside your bankroll after you set aside your reserved gp. Gear is never counted here.
Skills and quests: only the levels and quests you enter get checked. A method needing a skill you haven't entered goes into “Unknown, add your levels”, never assumed passed or failed.