I gotta say of all the torpedo learning problems I've had and issues I still fight with (duds, deflected torps, prematures...) the gyro angle has never been an issue. I've sat right between several columns in a convoy, fired two torps left, three torps right, and never turned the sub, all the torps went off on their projected paths and hit targets without problems! Historically I dont recall reading any books where they mentioned gyro angles as a problem either, but one thing I do read a lot and that's not in the game is the time it took for the TDC to send the settings to the torpedo. For us it's instant, for the real guys back then they had to input the settings then wait for it to get set before they could fire. Not a big deal, but maybe that'll be one of the changes for SH4?

I almost exclusively use magnetic but for extreme circumstances.

Set depth to 1 to 1.5m below their draft and watch the fireworks.

As you progress up the realism chain, the first thing I recommend you take on yourself is manual torpedo targeting - it is probably the most enjoyable jump in gameplay, whereas some of the realism settings (in my opinion) really just add difficulty. (The 100% realism crowd will quickly point out that difficulty is in itself a source of fun, but I still struggle without map updates as an example).

The "soft landing" for torpedo realism is the "fast 90" method as outlined in the stickied newbie area, because then you don't have to estimate AoB. Try it out - it isn't very hard, but it sure adds another dimension of interesting gameplay.