Nominally, you are allowed one bag each, plus the following:
Quoting from https://www.sata.pt/en/useful-information/hand-baggage
In addition to the cabin baggage allowance, passengers may carry the following items free of charge:
One overcoat, a coat or one blanket;
One umbrella or one walking stick;
One photo or film camera of small dimensions and/or one pair of binoculars;
Books and magazines in a reasonable quantity to read during flight;
One diplomatic handbag type or a bag with one laptop;
One lady’s small handbag, a wallet or a purse whose dimensions are in accordance with the normal wear for the flight and did not contain articles that may be considered as baggage;
*Passengers travelling with babies: one portable basket, food and clothes to be worn during the flight;
*Incapacitated passengers or passengers with reduced mobility: a collapsible wheelchair, one pair of crutches, prosthetic devices or other articles considered indispensable for his locomotion;
*Deaf or blind passengers (partial or total): a guide dog travelling with passengers since a pre notification has been done and confirmed.
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When you say "a backpack", I'm not sure if you mean a small pack that only carries your reading materials, or something that comes close to carry-on size limits. If it's the former, I doubt you'll have trouble. If it's the latter, they may let you through, or give you hassle, depending on how they feel that particular day.
One thing I tent to do to maximize my carry-on capacity is pack any camera related gear in a separate bag, with some clothes used for padding. It will not matter to those with small cameras, but an SLR with a couple of lenses is not only somewhat bulky, but it's also fragile and expensive and no airline is going to force you to check that stuff in - because they know chances are it's not gonna come out fully functional at the destination and you'll be upset and hassle them over it.
In general, many people do go over the official limits and the airline staff do not make a big deal out of it every time. However, the overhead bin space is running out by the time the last batch of people board the plane, so I do expect them to start cracking down on people with 2-3 big bags sooner rather than later.