There are two issues here - one aesthetic and one practical. If you want to see what JG'ers use as background information, look at Saito's "Magic of Trees and Stones", available in many libraries. It is old (1964), but the best English language treatment. He generally says that 12" is the minimum, greatest dimension should go across the path, and the stones have to relate to each other (paralell irregular edges). It sounds like you have a plan for a standard width that has irregular stones inside the edging but not "paving" the full space. This is outside of typical JG designs, but you can find many books with ideas to build from.
Practically, I find that when individual stepping stones are much less than 25 lbs, they are too easy to shift. Stones can be 4 or 6" thick if they are buried to leave only an inch or two above the ground. Stones that are 18" wide and a foot deep and 4" thick will weigh more than 50 lbs. The best are stones that weigh as much as the person walking on them - they rarely shift. Use a compacted base, pound in the sand around the stones, and use something other than sand to top it off if you want moss to grow. I use a clay subsoil that compacts well and holds the moisture for moss very well. Good Luck.
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Great advice on how to lay pavers
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