So far my profile is hit and miss. Even when using the keyboard I find that I have to press and 'hold' a key many times for the game to see it. Maybe my pc is too slow. But pressing TB buttons is also hit and miss, and not very fun therefore...
Don't know about online. Have never done that.
But you need to do some quick missions to get into the fun of it quickly.
I have realism set to 46. I have Air, Fuel, and most of the other options on except for limited camera views and realistic targeting.
I only run on the surface during the night, and that is at 2/3rds speed to save diesel.
I run at periscope depth during the day at 1/3rd to save batteries. If planes get to be a problem I dive deeper so they can't see me in the water. (I think they can see like 20-30 feet deep)
Use silent running (get the mods that put it on every stations toolbar) when avoiding detection. But you cannot reload tubes in this mode, so you must wait. Turn it off when you are safe. You'll usually forget without that mod.
Use high time compression, along with surfacing at night and diving at day to get to your location. I run on the surface all day when in friendly waters until I get attached by planes, then I consider going under during days. This part, going from point A to B get's boring and is what mainly gets me bored with this game (ie. SH3)
www.subsim.com is the place for downloads and forums.