First NAS build. How powerful hardware do I need?

I'm new to this as well. But after loading and reloading over the past week and 1/2. I've learning that this OS runs just fine on some low end hardware. I'm sure 8 or 16Gigs would be plenty for those 2 things you going to run. with a small SFF your most likely not going to be able to install more than 1 Hard Drive. So your most likely will be booting off a USB which is fine. It just means OS boot would be what it is. I think you should try stuff with 8Gig's and if its just using too much resources then bump up to 16gigs. Also cool thing I found in this software you can limit your docker in how much memory it uses per a container. I thought that setting was pretty cool.

I'm running an old i5 and 8GB RAM just fine, with SSD system disk and 4x 3TB HDD's.

Plex, Qbittorent, Transmission and Bubble UPNP server present in Docker.

Did not noticed any problems, stats shows, there is still plenty reserves...

As everybody mentioned, CPU is not the bottleneck.

Memory will be eaten up with the number of applications running in docker containers.

For me : OS + 30 containers = around 5GB

(not bad.....)

If you want a benchmark to reassure yourself how little grunt OMV needs to run well, I'm running 4TB with an ancient i386 intel Atom @ 1.6GHz passively cooled micro board with 2GB of DDR2 @ 800MHz. It's a lightweight setup mainly used for SMB, FTP and as a Plex server. I transcode all my media prior to upload to save repeated CPU grind so all Plex has to do is stream.

Everything is silky smooth because Debian will run on anything and I could probably power the whole thing with a potato.

MaxNewbie are you still alive and well?

I'd hope for a response.

Performance bottleneck is usually the network (NIC in computer, router & WiFi), as shown in the performance benchmark results linked in my signature