Value of 1x4 Lathing over Plywood Deck

We are in the process of removing the old composition shingle roof and having a clip-on standing seam roof installed. I think our installation is fairly simple and the contractor is competent, so our issues are minimal. But there are a couple of things we don't understand and need expert help on. We have a very simple gable end house with a 7/12 and 5/12 pitch roof on each side. The attic has free flowing ventilation using continuous soffit vents and a ridge vent. The deck is plywood and has a foil backing on the attic side. This foil was a specially applied item on the plywood at the time of the house construction. The existing roof is an Elk composition/asphalt shingle at 22 years of service and is finished. We live in humid Texas near Houston where the dewpoint is almost fog in the mornings, and there are trees and pollen coats everything in the Spring. The 1st question involves the use of 1x4 lathing on top of the deck so that the metal is not in contact with the plywood deck. Our assumption is that the space will reduce the heat gain into the attic. Is that correct? But, have we created an air gap and more condensation that would affect the wood? The lathing is not treated lumber and against the metal. The lathing is installed crossways along the roof so there is not a free flow of ventilation. The underlayment is Titanium 30. So, the question is, is it BEST to use the lathing or not use the lathing, long term? The 2nd question involves the color choice for the roof. The contractor recommended the uncoated galvalume since it is the most energy efficient. However, we do not prefer a shinny roof, but we do not know if the shinny roof will turn a dull gray over time. But, if we bought a painted light gray coated roof, would it be significantly less efficient on the heat gain compared to the dull-shinny roof over the long term. Doesn't the reflection of the "shine" work even if it is below the paint coating? So, the question is how less efficient is a light gray coated roof compared to a shinny roof?

Thanks very much for the information. I understand what both experts have said and can make the necessary adjustments in the plans. There is one thing that is not clear and I do not know if it is terminology of the industry or a mis-type. It is the term " 'reduce lathing read through' use a panel that is either stucco embossed or has striations in the flat areas". Are your referring to the potential rot of the wood lathing from condensation of the underside of the steel panel, and this can be reduce by having a slightly irregular contact surface? Does that mean that untreated wood installed on top of the underlayment and in direct contact with the sheet metal roof may tend to rot? Thanks very much for your information and getting me lined up to replace the roof.