If you want x86-64 support in fanless, take a look at Celeron (low powered) based industrial PCs. Qotom comes to mind. You can get a passively cooled machine. Most come with a NVMe and 2.5 slot for storage, do doing raid 1 is possible without external storage. I've bern running my J1900 based one for nearly 5 years and haven't had an issue with hardware at all.