Exactly right, the first four are algorithmically generated at lower frequencies and then we switch to band-limited wavetables before aliasing becomes audible. There's a bug in there where I normalized the octave wavetables separately without realizing it would change their relative perceived volumes, so at some places you can hear a small jump in volume as you change frequency. One of these days I'll go back and fix that.
The noise waveform is LFSR, yes, with the frequency parameter changing how often it jumps to the next value. I probably got that from the old school video game chips..
As for the PO synths, I honestly have no idea! Years ago David from TE sent us some Pocket Operator code without any explanation and I patched it in. I could spend time sorting out what's going in there and trying to document it, but I'm not sure that would be any more useful to you than just sitting down and playing around with the parameters.
The sound engine has a lot of features that most game devs don't even touch, but they're there because I love this stuff so I put them in. But since they're hiding in the corner we don't get as much feedback and the code isn't tested as well as the rest of the API. I wish I had more time to focus on this part of it but there's a lot of other work to do. One new thing coming up in the next release that I'm really excited about is wavetable interpolation, vector synth style. It's a really simple but effective way to add motion and dynamic control to synths, like FM made possible but without being a huge pain to program.