I actually run my arrstack on a Synology, it has official support for docker and docker-compose. Granted I do have a higher powered model (the DS1621xs+) but most of the arrstack is fairly low power friendly.
You can also get away with running Plex on a nas but I would only do it if 1. Your nas has a quick sync supported CPU and you get that enabled properly or 2. You go the direct streaming only / no transcoding setup - which means checking the codec support for all client devices and either only downloading exactly the supported codecs or pre-transcoding everything.
What I do is actually run Plex/JF on a separate nuc and point it at the nas using a network mount. Just don’t use a network mount for the Plex app database (maybe same applies to JF too), just mount the media files itself. Running Plex and having it access the DB over a network mount is a big no no for various reasons.