searching for low idle-power MoBo + CPU combination

Hi, 

I am planning to upgrade my current Unraid server 

E5-1620 v2

D3128-B2

FirePro W7000

into a low noise, low idle-power HTPC-build (Silverstone GD07)., and I need some help because power consumption wasn't a topic for me before. But I want to keep my bills as low as possible and be more "green". 

Since this server will be running 24/7 in the future - I want to build it with the lowest possible idle-power consumption - BUT with enough power for everyday usage and some light gaming. 

I want to keep the GPU for now. 

Usage:

• 2 VMs (1x Windows for gaming (no AAA games) and image editing / 1x Linux for surfing and online banking)
• NAS usage (datastore, no media streaming)
• paperless-ng
• home automation docker
• pihole
• proxyserver
• as I am new to Unraid, there will follow some more dockers

I was thinking about the 3700x or 3600x, but I've read that AMD motherboards are not really power efficient. 

So maybe Intel? The power of the i5-10400 should be enough for my needs or should I better go for a more powerful CPU and undervolt it?

Motherboard requirements:

- 1 USB port on the motherboard for the Unraid-stick

- 1x PCIE x16 for GPU

- min. 2x PCIE x4 for 10GBE or USB controller or whatever will be needed in the future 

- no LED lighting wanted 

- form factor: Extended ATX, ATX, Micro-ATX (I believe the smaller the better)

An idle power of <=30W would be very nice. 

Thanks

Dorsch