But this is something that you probably do not want to store in DT.
“Images of spreadsheets” instead of the spreadsheets itself? Why? Images take a lot more space usually, are limited to the first worksheet unless you are going the extra mile there and do not permit searching (unless you OCR them, in which case you’d rather save the spreadsheet as such in the first place).
Which is not related to DT. If you’re serious about “forever”, you should be prepared for some heavy spending: backups in different locations, a strategy for copying the backups regularly on other media,
So you want to edit 120 RAW photos plus 9 hours of video on an iMac per week. Manually. The digital image data alone amounts to roughly 1,5 TB a week. Which means that your G-Speed eS 0g02324 with its 16 TB at Raid 5 will be filled up after three weeks (Raid 5 uses at least 3 disks, which leaves you only a third of the 16 TB. At best). And all that connected to a Mac (an iMac, as you said) with its not overly comfortable tools to manage disks, volumes and disk arrays.
It’s always nice to have fast disks – but in this case, you need RAM more than read/write speed, I suppose. You’re not editing on the disk but in the computer, and it needs to read/write the photos only at the beginning/end of the editing process. Videos are probably processed in batches, but even for them RAM is probably the most important resource.
But, as @BLUEFROG insinuated: All this heavy data lifting is not related to DT at all. And after having read your posts, I assume that more than a document management system, you need a workflow. Some structured process for it all. “Notes” that are flying around probably just don’t cut it. Unless you’re very well organized, which you stated that you aren’t.
And even more than that, you need a clear concept. Maybe a consultant. You are, as you said yourself, not IT savvy, but attempt a hardware and software intensive operation without any professional help? Excuse my language, but that sounds like madness to me. There are probably ready-made solutions out there in the movie industry – you might want to look at them. And maybe get a consultant.