I wasn't able to find time to attempt this during the contest, but I've worked through the full set on my own time since. I usually sit out on sudoku contests, but the theme here piqued my interest enough and I'm very glad I solved these. My favorite paths were the Little Killer and X Sums, though I also loved placing all copies of an unknown digit in the Kropki, twice, before deducing the digit set.
Wonderful puzzles across the board though, thanks for creating them!