How "much" CPU/RAM does one need to run Unraid smooth

So I read up about all the different Systems/OS there are out there and I think Unraid is exactly what I am looking for.

I currently have a Raid 1 System running, 4x WD RED 3TB with a useable capacity of 6TB in a HP N54L for my more "important" data. That will stay as is.

My other data is currently spread between 6 Disks and running on the following setup (on Windows 10, no Raid or anything, just the discs connected):

Intertech 4U 4129-N (should fit around 15-20 HDD's)
MSI Z170A Gaming Pro Carbon
Intel Pentium G4520
Kingston FURY DIMM 4GB, DDR4-2133 (HX421C14FB/4)
BeQuiet Dark Power Pro 11 1200W

What I have additionally sitting here:

LSI Logic LSI00301 Host Bus Adapter (SAS 9207-8i) with cables and adapters

What I am gonna buy:

16TB Toshiba Enterprise MG08ACA16TE HDD

3x 16GB Sandisk Cruzer Fit USB2.0 (SDCZ33-016G-G35) retail

So my plan is to use the 16TB drive as a parity drive, then add an empty 8TB drive as data disk and move stuff from one full HDD to the 8TB data disk. Then add the disk I just copied to the array (since I copied the data and it will be formatted upon adding to Array), and so on.

Is the Hardware (CPU/RAM) sufficient for running Unraid?

Do I need a Cache drive? From what I read the only downside would be that without a Cache drive the speed would be around 50MB/s

For now I also plan to shut down the server since I usually only switch it on every 2-3 month to move data (I use my "regular" PC which has around 15TB of "buffer space")

The plan is to expand the array once I need space/buy new HDDs to ~12 drives, should I get 2 Parity discs or is 1 enough?

Edit: I totally forgot, that is just to store the data and access it when needed, no streaming, no PLEX, no VM, no Docker for now, just storage with Parity and access via LAN

Edited September 17, 20214 yr by Stardust9876
added Info