Server not powerfull

Use one of the dedicated Player Apps instead of Plexweb:

Plex Media Player:

Or

Plex For Windows:
https://www.plex.tv/media-server-downloads/?_ga=2.20141944.1993529163.1575302888-1864473727.1455657109#plex-app

The link says ‘server’, select the app when you get there - Plex For Windows looks most like Plexweb, so you’ll never know the difference, apart from it being to play most everything you throw at it.