Does a DPOA suspend the grantor's ability to make their own decisions?

The DPOA authorizes you to act on the behalf of the grantor - NOT instead of. That would be a guardianship.
You do NOT have to accept any responsibilities - once again - you Can (are allowed to) - not you HAVE TO.

The POA carries out the wishes for the patient who cannot get things done.
The paperwork for POA states whether it is immediate or only in case of xxxx, and what events terminate the POA.
So if you have POA and grandma does not want to go to a nursing home, you can't send her there. In that case you pursue Guardianship in court.

No. And No.