Keep in mind that neither LWAMI or RA were designed for single player. 
You can "tame" both of them somewhat by editing your missions for a better single player experience.
LWAMI adds some updated (but old) models but also nerfs your sensor performance. LWANI also adds some limited changes to the game's data base.
RA adds a lot more capability to the game but assumes you've been playing DW since 2005 and you're just that good or just that bored with stock DW in multiplayer. The best way I've found to understand RA is to assume that after the cold war ended, the NATO navies all went into hibernation while the old Warsaw Pact navies.....didn't.
The balance of power has shifted at sea and now everyone is on a more equal footing and it will be up to
you to adapt your tactics.
The downside of RA is that the Quick Mission function is now, basically, un-survivable 90% of the time. Its best to see the Quick Missions as a simulator on shore where you go to train in new tactics or get used to operating a new platform. In other words, don't get frustrated if you're sunk. Use the exercise to figure out how to do it better.
The one hint I can give you with RA is that its well-documented. Read EVERYTHING that is included with each update. If you launch a wep that acts goofy or does nothing, READ THE DOCS AGAIN.
Also keep in mind that RA was not meant to be played by folks who are new to Dangerous Waters or submarine games in general. Its better to learn the game and its tactics by playing vanilla DW for a while and figuring out what's going on before you install RA.