Performance penalty for separating multichannel sounds?

I would like to know if there is any performance penalties if you would split a multichannel instrument such as a drum kit into separate channels instead of mixing and equing “inside” the plugin. In this case I’m talking about Groove Agent SE and Simon Philips drum kit.

Or is Cubase clever enough to not waste any resources on passing through stuff such as level and pan setting inside a plugin?

The extra outputs/mixer channels in themselves do not use any appreciable amount of resources.
So unless you start putting additional insert FX on the individual channels there will be no penalty.