If you are concerned about reliability above performance, I would suggest using a single raidz2 vdev instead. This would allow the cluster to definitely survive two disks worth of failure. I'll also echo the common mantra - RAID is not backups. If you really need the data, you need to store a second copy offline in a different place.

When I lived in California and did not have room for a server rack, I had a single home server with an 8-bay tower case. I used an LSI card with 2 SAS-to-4x-SATA ports to connect all 8 drives to the machine. I believe I had 6 TB drives in that NAS, though they are currently all out of my house (part of one of my offsite backups now). My topology there was 4x mirror vdevs, which gave me worst case endurance of 1 failure but best case of 4 failures, and at about 4x the IOPS performance, but with the cost of only 50% storage efficiency vs the 75% you would get with raidz2.

There is even raidz3 if you are very paranoid, which allows up to 3 disks to fail before you lose the vdev. I've never used it. As I understand, the parity calculations get considerably more complicated, although I don't know if that really matters.

It depends on what your plans for the storage are. If you're going to fill it with bulk data that gets accessed sequentially (think media files), then performance will be fine with basically any topology or drive choice. If you are going to fill it with data for training ML models across multiple machines, you need to think about how you will make it not the bottleneck for your setup.

One more thing to consider - you can get new consumer OR used enterprise flash for somewhere around $45/TB in the 4 TB SATA size, or the 8 TB NVMe size. Those drives will likely fail read-only if they fail at all. They will usually use less power, take less space, and obviously will perform orders of magnitude better than spinning rust, at somewhere around 3x the cost.

I am hoping to build my next NAS entirely on flash.