Depending on the matchup, melee sheik and pm sheik are different, but she still retains a lot of fundamentals. The thing about melee sheik is that she was the reason about 70% of the cast was unviable, because of her dthrow. By switching it with this new DI system, it's hard to say whether or not she's better or worse (bthrow usmash is sexy) but it does make a lot of her matchups worse, which in my opinion, is what makes her feel different from melee shiek. The crouch cancel physics in this game are more similar to brawls than melee's, making crouch canceling a more viable option for and against her, which I think would lead her to play more defensively. Some of the buffs they did with her were interesting, like changing fthrow's knockback to melee's bthrow, but they are not enough to make her as well rounded as she was in melee. Now that she is one of the few characters lacking a neutral game (which she should be), she needs to play a lot heavier on punishment with grabs than straight combos. Also, down special is a real move now, making up for a lot of things she lacked such as recovery, or a chain grab on starfox. Zelda is a lot more helpful on final destination on starfox, making it not as bad as a pick against them.
I've been practicing pit as a secondary since about novemeber and I'm maining him now, and as strange as it is to say, I really do think he plays a lot like melee sheik, possibly even more than pm sheik does.