If say I install an internal RID module on a DJI Drone will I be compliant for Part 107 flights OR do I need a Certificate of compliance from the FAA for the install?
My opinion is that if you install an internal RID that has a Declaration of Compliance listed, you would satisfy 89.115 Alternative remote identification.
Before you purchase, go here to see if this module is listed.
If the RID Module has a Declaration of Compliance (DOC), that's all you need. When you register the drone, you just use the module serial number instead of the drone's serial number. There is no need for you to get the DOC yourself, the manufacture already did that.