I just bought the cheapest "Grade A" drives I could find from eBay. This is not the reliable way to do it, but as I have a 3 layer backup solution anyway, I don't really mind the risk of a drive failure.
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.