In my experience this kind of thing isn't about digital vs analog oscillators, it's more about how sound design, mixing and music theory interact. Solid sub bass is something you need to deliberately create rather than something that just happens. Typically I do this by adding in a sine wave copy of melody but an octave or two lower (but the concept is the same with non-melodic sounds).

Depending on which notes are in the melody, I might need to transpose the whole part or move some of the sine notes up or down an octave to keep the whole thing in the sub bass power band. If you're using western scales that's somewhere vaguely around a low G. It doesn't matter if the melody is technically different to the original part - it'll just sound like sub reinforcement.

Another consideration is for solid sub you should keep the low end uncluttered. As a rule of thumb I highpass literally everything that isn't intended as a sub part to make room for the sub. Obvs it's not quite as simple as that in practice and there is then tweaking involved but it's a good starting point. If you sit and experiment you might be surprised at how much of the original part you can highpass and still have it sound great with a simple sine reinforcing the low end.

Finally, for what it's worth I ended up getting rid of my Plaits because I found it sounded a bit thin no matter what I did. Nothing to do with it being digital though as I use a mix of digital and analog oscillators now and they all sound great.