Help with i5-8400 NAS build

This is my first time building a PC/NAS so I am quite lost.

At this momment I have 2 Qnap NAS running:

  • TS431-P2 (AnnapurnaLabs Alpine AL314 with 4 4TB WD Red disks) that I use for back ups, store and Dockers (tvheadend, oscam, …)
  • TS 251D (Celeron J4005 with 2 12Tb WD Red disks) that I basically use for Plex/Emby Direct Play + max 2 transcodders, for Emby TV (also 2 transcodders), for running a Linux VM that I use out of home (for example from my job office or in job travels) and for VPN (QVPN or OpenVPN).
    I have installed a QM2-2P10G1TA ( PCIe Gen2 x 4 / 10 Gbit ethernet + 2 slot SSD NVME)

My final intention is to have only one NAS for all the above tasks, but firstly I want to try unraid, removing the TS431-P2, with the 4 4TB disks until master above tasks; if I goal, the TS 251D would stop and fuse with the unraid one.

So, the buil I am thinking about is:

  • Intel Core i5-8400: 139,90€
  • Cooler Master Hyper 212 RGB Black Edition 57.3 CFM CPU Cooler: 46,65€
  • ASRock Z370 Pro4: 109 €
  • Corsair Vengeance LPX 32 GB (2 x 16 GB) DDR4-2400 CL16: 133,81€
  • Storage: 4 disk WD Red 4 TB: 0€
  • Cache: 1 NVME WDS500G3X0C-00SJG0 (using the QM2 card): 0€
  • Case: UNYKAch - Caja Rack 19" 4U UK4129 Unyka Negra: 83€ + 4 fans (120 and 80 mm): 52€
  • Power Supply: Cooler Master Elite V3 600 W 80+ Certified ATX Power Supply: 42,99 €

In addition I have 2 noob concerns:

  • Taking into account IQSV table, my TS451D Geminy Lake processor and the i5-8400 have the same range of codec management, how much the difference of the benchmarks would be noticed?

  • pcpartpicke says that the power consumption will be about 168 W. Is this the power consumption at rest? My two Nas has aboyt 75 W, so, it is also important to me the difference.

Thank you very much and sorry for my english.