OK SO I'm going to answer my own question... only because I don't feel any of the answers I found in the community answered the question WELL?
The solution is simple, [but only solved in this ONE manner.. that I could tell?] : Just Manage your System Drive by accessing it thru the Apple emblem on the top left of your screen... then select "About this Mac" followed by selecting "Storage" followed by selecting "manage" [that last selection, seems to be only available for the system drive]
I need to give you a little background, that matters as to why my case seems pretty extreme. As it turns out, I have a LOT of iOS devices. I'm a Pro Audio and Video guy and am heavily invested in Apple. I think I'm dealing with with 6 or 7 iPads and 3 iPhones [only 1 phone functions as a phone the other 2 as video cameras] but my point is that all the devices have the maximum available memory [that could be bought at the time of purchase] and that memory was heavily used in capturing UHD Video data or playing large MOV. files.
SO, FOLKS!, that means enormous "backups" what makes me mad is that these iOS backups are HIDDEN in your "Users" folder! and I mean UNLESS you use the "Manage files" [thru the Apple Symbol at the top left of your screen...
---- YOU WILL NEVER FIND THESE FILES---
I tried everything I could even using "Terminal" to run "OmniDiscSweeper" that revealed a whopping 40 more Gb's [sarcasm] than all the other attempts which wasn't even close to the [around 800+ Gb's] of files that where un accounted for!
Lastly: I feel Apple needs to improve the cross referencing of their search engines in these community boards!! I spent all day trying to word the question in JUST the "right" way that FINALLY gave me a close enough result, to then find this Solution!
I HOPE this helps?? I suffered along, with very little" wiggle room" On my system drive and it NEVER made sense how little space was available on that drive because I [intentionally] use HUNDREDS of external Hard Drives and go OUT OF MY WAY to never store any "DATA" on the internal System drives [but only temporarily as a project requires?] so as to have a LOT of bandwidth on the system drive. It never occurred to me that all my device backups would account for 85% of my system HD's data!?! made worse that Apple wants to HIDE the backup data ?!?! GEEZ guys! Show us the GD files!!! it's OK if you want to make it "hard" to Alter that data.. but not being able to FIND it is just stupid [sorry]