There's a useful, official response from the Waves YouTube account in one of those videos above:
"For those who asked how is Waves Submarine different than LoAir, RBass, and MaxxBass:
Submarine is powered by Waves’ Organic ReSynthesis engine, which lets you radically manipulate a sound while maintaining the pitch, timing, and clarity of transients.
In a nutshell, Organic ReSynthesis strips the source to its core elements (carrier, pitch, formant, and envelope) processes them individually, and then reconstructs them to prevent unwanted artifacts and yield natural results.
MaxxBass and RBass are fantastic solutions for helping the bass in your productions become more audible on small speakers and earbuds. But these solutions don’t add sub-harmonics to your signal. Instead, they use a unique algorithm, that is based on psychoacoustics, to fool your brain into hearing more bass you're using a listening device that can’t reproduce low bass frequencies.
Waves Submarine is a different solution. It adds true sub-harmonics up to -2 octaves below the source to add impact on large speaker systems that include subwoofers. So think night clubs, live music venues, and movie theaters).
LoAir is geared towards post-production. It is used for enhancing and enriching LFE content of 5.1 sources, or for creating LFE content from mono, stereo, and 5.0 sources. LoAir generates subharmonics up to -1 octave below the source.
Waves Submarine is a precision tool that is geared toward a variety of use cases - be it music production, mixing, live sound, post-production, sound design, and even mastering.
Submarine’s Organic ReSynthesis technology makes it the ideal subs shaper, as it lets you add powerful sub-harmonics while preserving the pitch, timing, and clarity of transients. Additionally, Submarine offers a frequency range selector, that allows you to surgically add subharmonics only to a specific part of your source. For example, you can add subs to a busy drum loop. Lastly, Submarine generates subs not only –1 octave, but up to -2 octaves below the source, letting you shape your subs with more impact than ever before.
Whether you’re a producer, mixer, sound designer, or a DJ, Submarine gives you all the controls you need to precisely shape deep, flawless subs."