I was like you and had my Synology DS920+ doing everything - the full *arr suite in docker containers, Plex server (native), torrents (in container), etc. I've recently moved away from that to a new setup which I think will be significantly better and simpler.
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Mac Mini M4: this is running Plex Media Server and all the *arrs. I'm currently running them natively, but might move them off to docker. Don't really see any need to though, they're safe and I know how to configure them like the back of my hand at this point.
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Terra-Master D5-310 5 Bay DAS: running in RAID5 with 5x10TB WD Red drives. Since this is connected directly to the Mac via USB-C, so is essentially a external HDD, it can be backed up with BackBlaze for $99/year! This is great because it's just plain RAID5, not Synology's proprietary RAID (which is great btw) so I'm not locked in to their hardware ecosystem.
The Mac has absolutely no problem transcoding as many streams as you can throw at it, and the power draw is just insane. It tops out at like 50W or something stupid, and idles at about 4W.
What issues are you having with it? I just did this and have found it to be pretty much perfect.