For playback on a desktop, use Plex Desktop for Win/Mac/Linux (download, documentation). It is much more capable than Plex Web. It direct plays most formats, including HDR10 video and TrueHD audio.
With the Plex LG app, be mindful of the impact of using subtitles. With the Plex LG app, if the media is direct streaming, such as when audio is transcoding, enabling any form of subtitle results in a video transcode. This means avoiding subtitles when playing media with TrueHD and possibly DTS audio (LG dropped support for DTS in 2020).
Make sure you are running the 64-bit version of Plex Media Server (download). It supports hardware accelerated tonemapping with Nvidia GPUs (reference). Additionally, it supports zero-copy transcoding (release notes), which improves transcoder throughput, as the system has to move less data between the GPU RAM and system RAM.
You can install the 64-bit version on top of the 32-bit version. The installer will recognize the 32-bit version and uninstall it.
If you are unsure which version is currently in use, look at the installation location. PMS 32-bit installs in c:\windows\program files (x86). PMS 64-bit installs in c:\windows\program files.
