The cognitive load would come from unfamiliarity more than anything. It dissipates once you learn and use the system enough regardless of how you interact with it(assuming the UI is consistent and reliable, which far too many aren't)
It did help that I was mainly writing Go at the time which has the great vim-go plugin. Not sure how I would have done if I was writing mainly writing another language (C#, Java etc come to mind as perhaps benefiting more from a full-fledged IDE).