These contracts do not stipulate reimbursement for lost revenue. The “uptime guarantee” just gets you a partial discount or service refund for the impacted services.
It is on the customer to architect their environment for high availability (use multiple regions or even multiple hyperscalers, depending on the uptime need).
Source: I work at an enterprise that is bound by one of these agreements (although not with AWS).
I’ve tried both Unraid and TrueNAS. While I greatly prefer TrueNAS, Unraid is much easier to set up and get going for beginners. It’s been a while since I’ve set up TrueNAS from scratch, but last I tried, it wasn’t a very beginner friendly experience. If you weren’t already familiar with ZFS, you were in for a pretty difficult time.
I’ve never used your exact setup, but I have had issues with a web server behind a WAF not getting the client IP (all user traffic was shown as the WAF IP). In my case, the WAF was appending the client IP in a header, and I just had to tell web app to use that header as the client IP instead of the actual IP. Again, not sure if this helps since I have never used podman or caddy (this setup was with Wordpress and an Azure Application Gateway) but the same principles might apply.
I previously had a QNAP, and they honestly aren’t much better than Synology. I would definitely go the build your own route. For the OS, I really can’t recommend TrueNAS more. I’ve been using it for years and it is rock solid.
There is an iOS/macOS app called “Pi-hole Remote” that can manage multiple PiHole instances at once. I use that because it will make changes on both instances at once for me.
Other than that, I log in to each device and copy paste.