Not really following you there. I also don't recommend USB disks in the cache pool if that's what you mean. Dropped disks there are bad too.
You don't have to "preclear" any disks. The only purpose of preclear these days is to test a disk, and perhaps burn it in a little to get it past "infant mortality".
Unraid will clear a disk if it isn't already clear when you add it to a new slot in the array. Much older versions of Unraid this clearing took the array offline until it was done, so preclear was invented to clear a disk before (pre) adding it to the array.
And Unraid only requires a clear disk when adding it to a new slot in the array. It is not needed when replacing a disk, whether for failure or simply for upsizing, since the entire disk will be overwritten anyway. Clearing a disk is strictly for the purpose of keeping parity valid when adding a disk to a new slot, since a disk that is all zeros has no effect on parity.
As I said before, you can test a disk using the manufacturer's software. As for burning it in, some do and some don't. It is probably less risk to simply use a new disk with SATA than to try to use it with USB simply because you have not had time to preclear it.