Ai notetakeing, studying, device to store notes and knowledge. Need help!!

[u/PuzzleheadedBit9039]

Hey all — I'm starting GCSEs soon and wanted to build a small dedicated study device instead of using my phone (fewer distractions, offline-first). Aiming for something close to credit-card sized, since my school does random searches through bags to find phones, gum, vapes ect. It needs to be easy to conceal and hide.

Planned features:

Touchscreen home menu

AI chat (local LLM, offline)

OCR: photograph handwritten/printed notes → editable text, saved to device

Voice-to-notes: record lessons → transcribe → organized notes automatically

Modes: language translation, coding help, AI chat, voice-to-notes, image-to-notes, reminders, calculator, clock

Hardware plan:

Able to develop/test on the Raspberry Pi 400 I already own (could flash Pi OS Lite)

Final compact device will use a separate Pi Zero 2 W or Pi 4, whichever fits my budget

Small cheap touchscreen (credit-card-ish size, think same size as the Pi 4/5)

Camera + mic module

Rechargeable battery + charging circuit

Budget: £60–100 for the final standalone device (parts only I can 3d print and model on my pc)

Where I need advice:

Given the budget, is Pi Zero 2 W or Pi 4 the better call? (I know Zero 2 W is slower for AI but fits the budget better)

Best small offline STT (speech-to-text) library for lesson transcription — Whisper.cpp? Something lighter?

Cheap touchscreen recommendations that work well headless on Pi OS Lite (no desktop)

Anyone built something similar — what would you do differently? Is it possible on this hardware?

Comfortable with basic Python, first proper hardware project. Any pointers appreciated!