Nice work! Can't wait to see more of it.
Just wanted to chime in on the contact stiffness vs sliding attachments: Increasing contact stiffness does help with collisions and negate the use of sliding attachments, but I find that having too high a contact stiffness causes more problems with surfaces getting caught in more extreme compression.
Also for pressure and surface tension: Generally, I find that the suggested values of -2000+ and 30 respectively are way too higher for at least 3 characters that I've tried on now: Below -500 and 20 works better for me so far. I'm not quite sure if it's the scale of the characters that matters, but my solver scale is about the same size as my characters.