I have driven a single rudder fixed drive boat. At docking speeds you can only steer with the throttles and shifters (the rudder is useless) as you would a large yacht at idle speed you have limited menuverability with the rudder but any tight turns would have to be aided by the throttles.
It just take a little getting used to but is not difficult

Used to cruise in a 34' Tollycraft Sedan with twin Crusaders and a single fixed rudder.

Easiest boat on earth to maneuver, especially dockside!
You'll learn never try to steer with the rudder near the docks,
the engine throttles control all.

QUESTION however,
I wonder how twin outdrives would react using the engine throttle controls instead of steering.
Wouldn't it be quite similar at idle speeds?

Turning the wheel actually screws things up, I use the sticks 95+%.

I agree 100% of the time with you.

0% of the time with you.

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Just a joke. Look at posts 14,15.

So on a MTI it would take a bit off a learning curve to dock especially with a strong current.

Yes, not that difficult, but a current can sure mess things up in a hurry.
One thing it seems some are missing, is that with a true inboard (ie:cruzer) You have very large props that are under the boat. This is MUCH easier than a high performance cat with small wheels sticking out the back.

docking a big cat is like that new lexus with the auto-park compared to a full staggered v bottom with the props turning in...