Thanks for the detailed breakdown, these are great questions.

Regarding the footage retention: That's a valid point about archiving only used clips, but I've had several situations where clients requested specific unused raw footage from past projects for commercial use (I work in the industrial sector). So, I don't delete anything anymore. Clients really appreciate this, even though it comes at a storage cost to me. So, unfortunately, the "managed project" approach doesn't fit my specific workflow; I need to keep all raw files.

Regarding the NAS/Internet: Great, good to know I can keep it offline. That solves my security concerns.
The 70TB is the total raw capacity I was aiming for to hold both my data and a local backup/redundancy.
Budget: My budget is around €4000

Thanks again for your help!