350-370 Mb on idle sounds about right, but it sure can go up to 450 ore even more, with "goodies" starting by default. IceWM with a "luxury" setup that looks very much like XFCE drops this to 200-250 Mb, depending on how fancy I go. One of my lightest setups (Openbox without a task bar, no PulseAudio, no NetworkManager, no Picom, etc) can drop this to 130-150 Mb. And my weakest machine runs an Openbox setup with a ~100 Mb memory footprint on idle, without actually losing much other than the looks - I still have sound, internet, etc. Lots of shortcuts for pretty much anything make the task bar and fancy menus useless. Unless using mouse-heavy applications, I even put the mouse aside because it's useless.
A pleasant detail in this forum: several people pick a picture of their pet as their avatar. Who am I to do otherwise?