Typically the pros do not lay the drywall on the floor, it is leaned up against various walls so the cutting to size is done right there. The sheets are easy to finish standing to score and break backwards to finish scoring the other side. A large T square will be really handy here, it will really speed up cutting.
I strongly recommend using a bearing wall to stand the drywall against. If it is laid on the floor, it usually get walked on, corners and edges will get damaged. making the taping job a bit more difficult, or making more cutting needed. For the amount of drywall you have, use 2 walls to stack the drywall, arrange it so those will be the last 2 walls that need to be done. Usually how daylight comes into a room is a consideration here.
When bearing walls are used to lay the drywall against, the carrying capacity is greatly increased over laying it on the floor where the center of the floor carries the load. This would overload the span unless you make smaller piles, more piles to walk on.