If you are setting up a new tank I would just add the LR directly to the tank and let it cycle the tank. There will be some die off even if it's cured LR, uncured is better for this purpose.
You should inspect the LR before adding it to the tank. At the very least, swish it in a bucket of sw to knock off the loose sand, and debris from shipping.
Instead of mixing LR from the pacific and carribean I would suggest getting 50% base rock and 50% pacific rock (fiji, marshal island,Vanuati, Bali, etc.)
You had asked about the interaction of coral and LR. LR is the base to which you attach a coral. LR is part of your biological filter. The surface area hosts the beneficial bacteria that break down ammonia to nitrite, nitrite to nitrate, and in the deep crevices breakdown nitritate to nitrogen. That's one of the reasons I perfer pacific coral LR.