I use Plex Media Server to remotely stream my private movie and TV series library to different devices for myself and my family. I only use Direct Play. No downloads, intro skipping, etc. There are never more than three active streams at a time. Occasionally, I downgrade movie quality from 4K to 1080p if I notice any lag during playback.
Would the Remote Watch Pass be sufficient for my needs, or would it be better to get a Plex Pass instead? Thanks in advance for your help.
But yes, if all devices which stream from your server are logged into your own plex user account, a Remote Watch Pass would be theoretically sufficient.
Unless your server has a very powerful CPU, your server needs hardware support to do 4K to FHD transcoding. And that is only available with a full Plex Pass.