You are very incorrect. Dual loops are less efficient on all levels than a single loop. Single loops allow you to use all available rad space at all times,dual loops do not. Warming of components that are not being used is not even a concern so I'm confused why you would even worry about this. Rad efficiency goes up with higher fluid temps and has no relation to temperature glide across components.
If you want some 'credentials', I work at EK and have been doing this far longer than you.....