Are you on Windows 10 or Windows 11? There is a BIOS update for your machine so try applying that (Dell Update or SupportAssist should have it for you).
Since owning this laptop I've always noticed that the performance of the laptop is significantly worse when off charge. Playing YouTube videos in any quality higher than 1080p is virtually impossible and running any applications such as SkyGo, Amazon Prime Video, Netflix and Twitch again is virtually impossible.  The battery level decreases so fast that using the laptop off charge is pointless. Anyone else having the same issues? Any setting changes I can make to improve performance? 
XPS 13 9300 poor performance off charge