As somebody who flies KL 737s all the time, and has been doing so since they joined the fleet, I really should be able to shed some light on this. But I mostly fly on autopilot and only pay attention to what's directly relevant to me. However, there are a few things I can confirm:
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• J cabin comprises of a minimum of 2 rows on all 737 types (on all Cityhopper aircraft the minimum is 1 row).
• on the 737-900, the first two rows of J have these "tables" (actually gray plastic boxes) in the middle seats that provide a flat surface at armrest level with two circular indentations for beverage glasses. The other potential J rows lack this feature, presumably because they don't want to have to remove and store these boxes when those rows are sold as EC.
• Until the final position of the divider is determined at STD-72 the 737-800 configuration always comprises of J rows 1-5 and EC row 6 (the same, by the way, holds true for KLC's new E190-E2s, where only the first 5 rows have adjustable headrests).

The vast majority of my flights are on the 738, and none of my current bookings show a 739 scheduled, so I can't check, but if memory serves the standard 737-900 configuration is J 1-7 and EC 8-10 until STD-72. I'm pretty sure the 737-700 configuration is as for the -800.

Johan