https://www.modelfkeyboards.com/store/ is what I'm looking a for my next keyboard. I am typing this on a Keychron which I will agree with others is a great keyboard option for somewhat cheap.
For general computer stuff B&H. Though if I knew of a local store near me I'd be sure to support them.
Odds are strongly against a 2 drive failure at your scale, though it does happen. I set my NAS up about 8 years ago, with 6 drives with raid-6 (well zfs's version) and in that time two drives have failed years apart. When you get two hundreds of drives total in your operation you will see a dual drive failure.
Though you still really should have backups of everything you care about. Even though odds are in your favor someone reading this will lose data in their life on their NAS system.