Best setup for new PI4 Download Box

Like many others on here, I've finally had enough of the constant splintering of content into more and more separate services, each offering less value.

Anyway, so I have a new 8gb Pi4b on the way and I want to set up a "download box".

Ideally something fairly automated using NZBs. Years ago I used to use Sickbeard + SABNZBD+ on a small windows box. But I wanted a small, simple, ultra low power fanless box, so I've gone for a Pi4.

I'm aware of the *arr apps, although I haven't used any of them yet. I'm thinking a bunch of the *arr apps + SABNZBD+ and just keep using the Plex instance running on my Netgear NAS as the front end (got the lifetime Plex Pass). So I just need the download apps running in my Pi4 for now.

Question is: what do I put onto my Pi4 as the best base on top of which to build all of this?

Unfortunately I'm a Linux newb, so I want something fairly simple which can run all the apps I need and mount my NAS for storage.

What setup do people think is best for the Pi4?