I use the spring creek stabilizers when taking our toddler along over stretches of big, cold water lakes. They are very well made and well worth the cost for what you get.
The beauty of them is that they retract and adjust length with several detent buttons. I kept them fully retracted against the gunwales, sort of like sponsons, and in that position they do not interfere in any way with paddling or the action of the tandem canoe, and did not seem to add much at all to the windage factor. When retracted they barely touch the tops of moderate waves, in my tandem. They would slow the canoe down in big waves and might cause a problem there.
My thought was that if something unforeseeable happened to tip us, or something crazy happened like running up on a submerged log and tipping, I could easily extend the stabilizer arms while swimming, and thus be able to quickly right the canoe and get the toddler back on board. They also helped my wife relax about it.
I have also used them with a motor on the canoe because I wanted to make sure the motor did not go in the drink when I was first getting used to it. I have found that to be unnecessary.
They are no substitute for experience, technique, and prudent judgment. In most circumstances, including fishing, I would think they would be more of a hindrance than a help.