I have four BTAs in my reef - My green I have built a cave around his attachment but hes so huge that I have to use koralias to keep him off stuff. My RBTAs are surrounded by GSP which they hate and don't seem to cross - they also seem to keep the GSP in check. Some corals the nems ignore - some they actively battle, like euphylias (frogspawn, hammer and torches) and some like goniopora which they seem to avoid. In the end the BTAs always win - so its up to you to keep them apart - If you can add the nems first - let them settle in and add the corals to the remaining space. Allow for growth.
Here's a pic from a couple of months back - things are even bigger now.