I have Plex configured to do partial scans, but unfortunately due to limitations (in SMB if I remember correctly), you can only have so many folders before partial scans no longer detect changes, which means that some changes in my setup are not detected until a scheduled scan goes through every folder. To make things worse, there is also a bug in Plex (regarding Curl) that large libraries cause TCP port exhaustion, which was made worse in 1.19.X versions. I would love to not do scheduled scans, but it would involve breaking up my libraries and file shares past the segmentation that I already do (tv shows, movies, cartoons, anime, etc). After I broke about 70-80TB of video, things stopped scaling so nicely.
Also, your "seems like you are the problem, not Unraid" comment was not necessary. I only stated that Unraid wouldn't work for me, which it seems like it won't. I never bashed Unraid as a product, which I'm sure works great for many people, and don't feel I should be bashed in return.
One of the biggest selling points for me on Unraid was the ability to dynamically grow my arrays, which is why I was testing it to see the feasibility of moving over my fleet of servers to it over time. Having to purchase drives 8-12 new drives at a time can get rather expensive, especially because it usually ends with me buying another server as well. I didn't mind the reduced read/write speeds as only one server in my setup actually needs high performance read/write and I would have just left that one on FreeNAS, but the latency I saw above just would have killed it for me. Moving the entire fleet over to Unraid would mean I would be looking at 1.5+ hours for each forced scan, which would be unfeasible for what I would require.