...I would first test the actual disk transfer rate with crystal disk mark,or, similar program. 8 TB is a huge capacity and no SSD solution can provide that capacity without large expense. Perhaps you may want to limit your ACTIVE editing projects to faster ,internal SSDs and use the 8TB drive as backup and archive. Another words, in the laptop you would want 2 separate, fast SSDs at a minimum. One would be a "boot drive" containing ONLY the OS, programs and Windows page file. You can experiment by putting the " media cache" files and "cache files" on the boot SSD....there should be no performance penalty doing this and these files can be easily erased when a project is completed. PPro will just recreate these files if ever needed again,later. The boot drive should be a quality SATA III SSD like a Samsung 850 Pro, which has a much better write performance than the cheaper EVO model.
Next, the second internal SSD, ( SATA III,OR, the faster PCI SSD NVMe drive ), would be your "project drive" where all ACTIVE video clips would be placed along with the project files . When a project is completed, these files could then be moved off the second SSD and placed on the external drive for archiving.
i do not believe it is possible for the 2 hard drives in the G RAID box to reach 480MB/sec. The interface may have that rating,but, 2 spinning ,mechanical HDDs will probably top out somewhere over 200MB/sec. Be aware that in a RAID 0 if EITHER one of those drives fail, you lose ALL your data !! Modern SSDs are FAR MORE reliable than spinning, mechanical hard drives .
If you can live with 4TB as your "archive" and "backup" drive, you may want to consider CHANGING the RAID array in that G RAID box to RAID 1, where each hard drive is MIRRORED for redundancy to protect your data and do all your editing and exporting on fast internal SSDs.
Be aware that Samsung makes the tiny T3 external SSD drive which is available up to 2 TB in capacity and runs at over 400MB/sec read and write over USB 3. I have one and it works great !...barely bigger than a matchbook !!
....by the way.....you were a great Yankee !!
hahahahahahahaha! I know!