Hi edickenson,
Besides esthetics, the ability to have the sleeping surface at the height you want, or other personal preferences … the height of a foundation makes no difference at all in terms of performance or support.
The most important part (for those who are looking at a rigid slatted foundation) is that the foundation has a strong, rigid, evenly supportive surface with slats that are no more than 3" apart.
The organic foundation at PJ’s is certainly good quality and good value too (excluding any shipping cost that may be involved). There are also other foundation options in the foundation thread here. The Cozy Pure foundation is also good quality and certainly suitable for a latex mattress but as you say it’s taller. If you do end up buying from PJ’s I would make sure you get their organic one rather than the one they also carry which is much lower quality (which Mike S bought the first time before he exchanged it).
Phoenix