When I had the pros I used them in a progression of 1k, 2k, 5k, 8k and either 12k or 15k because I had them both. As you noted 12k and 15k are probably the same stone but they (shapton) branded the Japan only version 12k. Anyway, their 1k is a very aggressive stone and I liked to come off it onto the 2k which I felt smoothed the bevel out from the aggressive 1k.

I began with them doing pyramids using the 5/8 and it was painfully slow going. When a member named smokingtbird, IIRC, posted a Japanese grit chart comparing their grit ratings with the USA grit charts I began doing a pyramid with the 2k/5k and initial finishing with the 8k pro. This yielded much faster and better results for me.

The superstones have a 3k, which according to the J-grit chart, and in my experience, works a bit better at the low end of the pyramid so I used the naniwas more than the pros. Doing 3/5 and than going to the 8k. Here is the thread that t-bird posted with the grit chart.