The plane will likely be an ATR 72 prop. Binter used to be quite relaxed, but I haven't left Madeira in a few years now, so I don't know if circumstances have changed. I used to travel light and didn't use the overhead lockers, so can't speak to what bag sizes will actually fit. But I did see other passengers load their hold luggage themselves before boarding (door open to a waste height baggage space next to the steps on) and then just pick it up when they disembarked. So maybe that's the worst case scenario, if you would excuse the pun?
Possibly best to contact Binter directly to be sure now?
A quirk of the ATR 72 is that you board from the back, and the expectation is that you fill the seats from the front. So it's first on last off/last on first off, particularly on full flights between the Canary Islands. But I was never on an FNC to LPA flight back then which wasn't relatively empty - ranging from a handful of passengers to about half full.