I want to know how heigh is your deck? and what dimensions, such as 32's along the wall (parallel to the all) or the 16' side. Regarding as to attach to your house or not, it is your choice, if it is high, then, I would suggest to attach to the house because that would provide you extra strength for your deck, if it is low( lower than 2' at the highest point, and you do not need permit for it, i think), a free standing deck is ok.
As finding level, depending on the height of your deck, You could use 4X4 and attach beams to 4x4, this way, you have lot room to play with. If your beams are going to sit on the concrete footings, then, you might have some difficulties to find level because you have to find level before you pour concrete.
As finding level, depending on the height of your deck, You could use 4X4 and attach beams to 4x4, this way, you have lot room to play with. If your beams are going to sit on the concrete footings, then, you might have some difficulties to find level because you have to find level before you pour concrete.