We have an enclosed 3 season porch on our 1927 bungalow. It’s not insulated, but is weathertight. I’d like to put a wood floor down, but am thinking engineered wood floor to save vertical space (I’d rather it be flush or lower than the house) and deal with temp fluctuations.

Assuming I lose some space after leveling the slab, I have room for ~1 inch foam (eps? xps? poly?) and one of the engineered floating click floors. If insulate, should I still put down a poly sheet first?  Anything between the insulation and the flooring?

Most of the brands I’ve looked at say they need to be maintained >50-60 degrees. Is that strictly necessary or just a rec? Wouldn’t floating it mitigate issues from temp fluctuations?  

Are there other/better assemblies I should be thinking about?