Something between would be TMOwTw,
Trigger Maru Overhauled with Training wheels
As for depth charge splashes, someone made a mod for that (no download links that I found), but it's not in Stock, unless you're using the original SSI Silent Hunter... TMO has it, correct? As for the hydrophone operator, if you're early in your career, they have no experience, and when you put on the phones, you're at a disadvantage if you encounter any vessels traveling at less than half of their maximum speed, you'll not hear them.
GFO, even though it's basically the Stcck game, with some of Webster's tweaks can be quite a bit of fun. Just don't expect too much traffic early in the game in any of the mods. If you want a dearth of traffic, try RSRDC. Downright anemic comparitively, unless you know where to look. Stock and TMO are similar. You just gotta find the traffic lanes. Think "oil fields" and "Japan"...