NCM install on existing multi poller NPM.. what the + -

Hi

We plan to deploy NCM the first time on existing setup that has NPM +2 pollers.

Core NPM 11.1

Plan to install 7.3.2 or 7.4

The qustion are:

Can I just install NCM on the primery and run operation on node that are being polled  (NPM) by APE?

Do I need to install in theAdditional Polling Engine (Advanced)Mode only if can't reach that node target  from my primery with NCM port (SSH /TFTP)?

Where are the  advantages with the install on the  other  NPM APE  (expect the load sharing)?

/SJA