One thing, NO ONE can multitask. It's impossible and has been proven. ONE activity will get the attention and the other will not. So, when it's critical, I could argue to pay attention to what's most important.
Sure, you can bounce back and forth with some degree of success, but still ONE gets the attention. Now, you CAN keep an eye on things and talk, to your mate or one the phone. But could make a strong argument for a hands free devise and limit cell conversation to non busy times. Yes, there are many times where the cell is appropriate... checking on someone you can't radio, making a marina reservation (most of them don't respond to email), checking fuel availability, reprovisioning. However, if you're really doing a lot, I could argue to give the helm to someone else.
As for looking at chart plotters, I could argue to know your plotter well enough so that you just glance at it when needed. Set your course, route, etc., during non busy times.
And, yes, and autopilot is almost like another crew member.
Fortunately, there's a LOT of rather open spaces, even in the ICW, and even on rather busy days. So there are sometimes that you can be a bit less focused.