AOOSTAR WTR MAX 6+5 Bays Desktop NAS Barebone， AMD R7 8845HS CPU, 2 * 10GB SFP+ 2.5GB LAN Ports，USB4&Oculink Port，Support ECC RAM, 2*DDR5 5600Mhz Slots，5* M.2 NVME Slots

Mobo https://www.asrockind.com/en-gb/IMB-X1314 You already have the RAM. Let the NAS just be a NAS https://a.co/d/0glAFjdm

You need the Aoostar WTR MAX. Smaller than your size restrictions, 6 3.5 bays + 5 NVMe. Good horsepower and up to 96ecc/128non GB. https://www.amazon.com/AOOSTAR-WTR-MAX-Ports%EF%BC%8CUSB4-Port%EF%BC%8CSupport/dp/B0G6BK4ZW7