Closed hand picking question

Recently I switched from open hand picking to closed hand picking because my pinky and ring finger keeps touching the knob. I am just wondering, when using closed hand picking should I float my hand on the top of the strings or rest my lower part of my thumb(between the thumb and wrist) on the strings like the picture below? 

Or to be more specific, should I float when playing around lower E string, and rest when paying around high E string?

It depends.  If you are playing single note lines on the high strings then it's helpful to keep contact with the lower strings to mute unwanted sound.  But if you are playing a looser rhythm part you'll need to keep your picking hand more floating while your fretting hand does more of the muting.

In short, you should practice both floating and planted because you'll need both depending on the musical context.

Hope that helps!