I'm not 100% sure but I think Minato couldn't "absorb" all the chakra when sealing Kyuubi therefore he only sealed half of it inside him. RDS can probably seal anything as long as the user can withstand it(more chakra the opponent has, harder it is to seal him completely).i would say its reaper death seal.. from what we have seen..
however im sure there must be stronger seals since there was a seal capable of sealing the whole of the kyuubi into a host which RDS couldnt do...