The interior of aircraft and the seating fit, seat pitch and width is entirely the airline's decision. The difference in each airline's approach can be quite considerable. Not all of them are as opulent as this
https://www.youtube.com/watch?v=GcK5...=TL04ODCqhmTJg
It is likely that air carriers choosing an aircraft for its frugality are not going to throw that away with a seating fit with reduced pax load. At the same time there are some 'lay flat' bed designs that are poorly thought out. Virgin 330's in business make it impossible for people to sit together and their beds have everyone's feet in the aisle. The filing cabinet draw approach of Delta in their 76's seems to be a better bet if a little claustrophobic.