What are you trying to accomplish? How critical is your 24TB of plex data to you?
One of the key benefits of the small all-in-one NAS boxes is typically data resiliency through some kind of RAID technology. I.E. That way if I have a (1) out of (4) 6TB drives fail, I still have access to that data.
In terms of what you should look at… the answer is… IT DEPENDS…
Are all your Plex clients local or remote?
What kind of plex clients do you have (TV’s, Streaming Sticks, etc.)?
How many concurrent streams will you be handling?
What is your upload bandwidth on your ISP?
What kinds of media are you playing (4K, HDR, 7 channel audio)?
Do you deal with subtitles?
All of these things can have an impact on how powerful of a NAS or not you need, especially as it relates to transcoding. Since you don’t have a plex-pass subscription, you can’t leverage the HW accelerated transcoding so you are putting additional load on the CPU of your Plex Server (if you need to transcode)