Will or Nomination? are they both required or is any one of the them good enough to transfer the deceased amount to the legal heirs

I would like to ask a general question for multiple financial instruments. Basically the concern is to have a hassel free transfer of money from deceased to legal heirs in case of the death of the deceased.
1. Is it ok to have a WILL and not have a Nomination?
OR
2. Is it ok to have Nominations for all financial instruments and then not have a WILL?
OR
3. Are both Nominations and WILL equally important to have.

Thanks,
Swapneel.