The experience for setting up an Mbin server has greatly improved with the latest Docker setup rework. So now, it shouldn't take more than a few minutes to get a simple Mbin setup running.
As for resource usage, my server (kbin.earth) doesn't have anywhere close to the user base fedia.io does, but I've been able to run my server (which has ~150 active and ~600 total users) on a decently low-resource server. In the past month or so, it's been a server with 16 vCPUs and 32 GB RAM, but previously it was running on 8 vCPUs and 16 GB RAM (had to upgrade due to DDOS).
I've been running my server for about 1.5 years (since December 2023), and most of the time it is a set-and-forget type of thing, of course, until you need to update things or troubleshoot some issue. But overall, it's been working great, and when you do run into an issue, the Mbin devs are usually quick to help troubleshoot with you.
It is true that Mbin doesn't have an "official" instance, but there are multiple servers that are run by the Mbin devs, including thebrainbin.org, gehirneimer.de, and kbin.melroy.org (and kbin.earth if you count me).