well, i've had both in a refugium before and the green overpowered and choked out the red.
the caulerpa is just a more aggressive grower.
it's not going to hurt anything to have both in the same area, but i suggest a section specifically for the red algae.
if you want to keep it as a food source, then just use a basket..float it in the sump, and put the red in there.
if you just want some different color in the fuge, it's not going to last i fear. this stuff seems to want to float to the bottom. the caulerpa will block the light from it eventually.