score:2
You can never know for sure. It is random allocation. They usually allocate the middle seats first. I recommend doing it a few hours before the flight. Especially with a mobile boarding pass you will be fine.
Most of the middle seats will be gone, so you will have a better chance of either a window or aisle seat, or a luxury seat with extra legroom. This has worked for me before.
From this guide:
My recommended Ryanair check in time is 2 hours before your flight if you're non-EU/EEA. If you're EU and have your boarding pass, then 1.5 hrs SHOULD be fine if it's not high season and a busy airport.