As far as Red Line Water Wetter....
They offer a "Diesel Water Wetter" and "Water Wetter".
What I have seen on store shelves is "Water Wetter", which is formulated for use in pure water cooling systems.
Some have noted that, when used in systems with Antifreeze, the Water Wetter can cause a scum to appear on the top of the fluid in the overflow bottle.
It seems that some separation can take place when the fluid cools down......and it is supposed to mix again when the fluid gets hot.
If you are using it in a "street" application with an antifreeze mixture (not just water), I would recommend that you look into the Diesel Water Wetter as it is formulated for use in a antifreeze system and as such, "should" not have the separation issue.
BOTH products are intended to improve the heat transfer between metal and the cooling fluid (either just water or a coolant mixture).
This would be in the engine.....heat transfer from the motor to the coolant. AND in the radiator....heat transfer from the coolant to the metal of the radiator.
THIS is what Red Line states that the product does.
NOTE! The coolant temperature that you see indicated from the coolant sensors "should" still stay about the same because the thermostat in the engine will STILL regulate for the same temperature.
THIS is a link, directly from the Red Line Oil website.
It is the "Technical Information" tab.
Under "White Papers", they list the information for both "Diesel Water Wetter" and "Water Wetter".
http://www.redlineoil.com/techinfo.aspx
Under the "Product Data" grouping, they list the Motor Oils lined up side by side so that you can compare them.
They also list the Transmission Fluid that you mention.
At the bottom left corner of their web pages is a Title "Company".....with several links.......including "Contact Us" which you can use to send them any questions you may have.
They have been reported to be very helpful.
I have used their motor oils, transmission fluid D4, Power Steering fluid and their S1 Fuel System Cleaner.
As a side note.....most fuel system cleaners, that you add to the fuel tank work BEST when they are in the system for a period of time.
In other words.....if you are on a trip and filling up several times through the day......the fuel system cleaner will not be as effective as when you add it where it will be in the system for a week or more.