He cannot inhale or jump.
Well, little correction... He can jump, he can slow his falls (though he turns into a parachute instead of puffing up)... he just can't inhale enemies, puff out air as an attack, or puff up to jump multiple times in mid-air (since he's thread).
Instead he uses his thread abilities to destroy enemies in a much simpler more plain way than before (though, transformations make up for that). The one real biggest difference (besides being able to slam down without turning into rock kirby, which reminds me more of SSB than old Kirby games) is IMHO it's much, much, much harder to even get injured and die in the game..... really, does this game actually let the enemies kill you? I sure never got damaged besides perhaps in a boss battle...