What is the typical/maximum output (BTU/sqft/hr) with a 1/2" pex heat transfer plate sandwich over wooden subfloor covered with thinset and tile?  What floor temps are we talking?

Does one tile type perform better than others (i.e. ceramic, granite, marble etc)?

Is a standard to go with only thinset or do I need backerboard?

with tile? you can max it out (i.e., make it uncomfortable to walk on) before you hit 40 BTUs/sq ft and 130-140 degree water temps, typically.

the difference in tiles is not worth thinking about.

I have seen every tile detail ever developed used over sandwiches and they all seem to work.

105 F floors seems comfortable.  What kind of output should that produce and at what water temps?

Can you point me to some data (charts, tables, graphs) with floor temp, output and water temps? 

that is wildly too hot. you do not want to break 90 deg F.

and if you find charts on sandwich, please share :D

radiant floor output is ballparked at floor temp minus room temp, times 2, in BTUs/sq ft. so an 80 degree floor in a 70 degree room should put out just about 20 BTUs/sq ft. approximate of course but close enough.