PiHole is great but as it’s a DNS server, if your unraid machine is turned off then you have no dns and cannot reasonably use the internet. Luckily you can run two instances - one in a container and another on a raspberry pi (or any other machine) so if one of them goes down then you still have DNS. Then you can point your router at both - you always have two options for DNS, the second being a backup, or used for load balancing. Even Google and Cloudflare provide two DNS servers.
You need to maintain both simultaneously so they have the same blacklists and general settings. There is another service called GravitySync that handles that for you but I’ve never been able to get that to work.