Hard Drive purchase question

Im working on a doc and shooting in 4k. I already have amassed 6 Tb of data and I still need to shoot a few more interviews. My questions is whether I can store media on an external drive and use another external Thunderbolt drive to store my FCPX projects and renders.-Im wondering also should I but another/bigger drive to store all media and work from there. I thinking I will have about 12 Tb when all is said and done. This Gh5 footage shot in ProRes on a Atomos recorder in ProRes422....thoughts

I have a 16TB Pegasus RAID (12TB usable) and love it. Remember, whatever you get, you'll want two, one as a nightly backup.