My two cents:
My wife and I paddle tandem and love it.
We have been doing it for years and we paddle in perfect sync.
We paddle for pleasure and we also race which is another form of pleasure for us.
Whatever paddle is most comfortable for you guys is the one to use, but before you start trying to figure out if you like a bent shaft over a straight, or vice versa, make sure your paddles are the CORRECT LENGTH. That is more important!
Someone above stated that “straights are for sitting or hit and switch”, which is wrong. I don’t believe there is a marathon racer around that doesn’t use a bent.
“Sit and switch” is with each of you paddling on opposite sides and in synch, (that is our preferred method). You as the stern paddler call a “hut” if the boat starts to turn or about after every eight strokes if it is maintaing a straight course, and you both simultaneously change sides.
You are probably a stronger paddler than she is, and it will probably start to turn after three or four strokes.
If there is a strong quartering wind, you might want to have her “hut” to the same side as you for short periods to off set the power of the wind.
On the front and back positions: for years and years, my wife was in the bow and I was in the stern, and we were happy paddlers. Then when we started racing, we were informed by the books that the power paddler should be in the bow, and since I was more powerful than her we switched places. That turned out terrible, and all we did was argue. We came close to giving up tandem paddling. After about a year of not enjoying paddling we went back to our old positions and for many years now have been happy paddlers and happy racers.
We used straights for the many years prior to racing, and then when we got into racing we switched to bents. If you want to go fast, (race) a bent is a must.
After getting used to a bent, we would never go back to a straight, and when we are just lilly dipping we now prefer the bents over the straights and can do every stroke and or correction with the bent equally as well as with the straight.
It is your job in the stern to keep in sync with her in the bow, since she can’t see you, but you can see her.
It is also your job in the stern to pick and maintain the course with minor corrections such as sweep strokes and J’s, (rudder strokes), or call for sweeps with both of you on the same side.
After you guys get proficient, get a book or talk with someone who has been paddling tandem for many moons and she as the bow paddler can learn how to make major corrections, such as “cross bow rudders”, “draws” and “Posts”, etc.
I know I have written a lot, but the main thing is for both of you to be HAPPY PADDLERS, and whatever paddle is the most comfortable is the one you should be using