I'm getting confused with the NS documentation. Our inventory is purchased, no manufacturing at all. Users want to utilize demand planning. Do I need to use MRP for supply and demand plans? The goal is auto po creation for supply orders.

Yes you would need MRP for the supply side. NetSuite is deprecating the previous version of supply generation and moving it to MRP.

Will reorder points still be available?

Yep, but it doesnt consider demand plans