The main difference between early and mid stage is, that stacks are now shorter, often around 30BB or even less in turbos. Shorter stacks increase the value of stealing blinds, and it also influence hand selection. For instance the value of small pocket pairs go down, and for this reason these hands often need to be folded from early position, or if someone else already entered the pot. There is also less room for drawing after the flop, so many things change, when stacks get shorter.