Here is some noise level info on Exos https://nascompares.com/2021/05/28/hard-drive-noise-seagate-vs-wd-vs-synology-and-toshiba/#Seagate_EXOS_Data_Center_Hard_Drives_-_Big_Loud_but_Surprisingly_Affordable
And it's more about luck there, some drives are working quietly some of them are not. Also, clarify about warranty for all drives. You can be suprised by Toshiba warranty which wouldn't cover your region.
Just get a synology NAS, it looks like the most decent option which is pretty intuitive and also easily to setup.
It will be okey, as soon as you power on the SSD and check the data time to time.
Unfortunately, it's not supported in mdadm. As an alternatives, you may look into zfs and btrfs. Also, backups with versioning may help you if bit rot happened to restore a good version of your file.
To add, Black friday is soon, so maybe it worth to wait for it.
Wait for for it. They should have the sales, however, if they wouldn't have the sales, probably, other sellers would have it.
Return it.
Recertified drives have limited warranty and new drives have a full warranty.
I wouldn't expect both external SSDs and HDDs to last more than 3-5 years.
Huge capacity.
What is exactly capacity? Cuz external SSDs have lower max capacity than HDDs.
In the end, the best option is to have backups!
As alternative to TrueNAS since the network storage is the only requirement, you may use Starwinds CVM without HA option. It is not over-provisioned with features like TrueNAS and no need to flash RAID controller into IT mode. Just miss the steps regarding HA and replication. https://www.starwindsoftware.com/resource-library/starwind-virtual-san-vsan-free-configuration-guide-for-proxmox-virtual-environment-ve-kvm-vsan-deployed-as-a-controller-virtual-machine-cvm/