Baby octopus is the best option considering it shall be much more tender and easier to work with.
The traditional recipe from Galicia wherein the dish is called Pulpo á Feira, which denotes Octopus Festival Style.
A 3 pound or 1.5 kilo baby octopus
8 garlic cloves minced
2 1/2 tsps sweet smoked paprika
salt and black pepper
1/2 cup or 4 fl. ounces of extra virgin olive oil
chopped herbs: parsley, dill
1 medium onion
*** to serve on wooden plates is traditional here in Galicia
1) in a stockpot, fill with water and salt and boil
2) take the octopus, and put a hook in its head, and dunk the animal five times in the boiling water - to tenderize
3) then, you shall be able to clean it; remove the eyes, and mouth sections
4) rinse thoroughly
5) place the octopus in boiling water with 8 fluid ounces of water to cover octopus and cover with lid
6) simmer for 35 mins for a baby and up until 1 hr and a half for larger than 3 pounds
7) check with a sharp knife and if tender, it is ready
8) remove from stockpot and set aside, and let cool
9) when it is cool, rinse again and rub off fragments of skin
10) mix the garlic, seasonings and olive oil and pour over the octopus
11) slice in 1/ 2 slices and place on wooden board or wood plate
12) season with the olive oil with herbs and sprinkle Smoked Paprika
13) serve with boiled potatoes with olive oil drizzle and smoked paprika
It is a lovely tapa, and would be great if you could serve with a Galician white wine; albariño or Portuguese albarinho grape variety white.