RealTemp GT is for the 6 core CPUs. The Core i7 in your Surface Pro 3 only has 2 cores so the regular RealTemp.exe is for you.
There is also an updated version of RealTemp available. It has a few more features for the newer Core i7 CPUs like you have.
RealTemp T|I Edition
https://drive.google.com/open?id=0B0dpSo9k93jDZlpmbHNzeFlpcWc
A difference of a degree or two between different temperature apps is normal. Most of these programs only update once or twice every second. CPU core temperatures can change much faster than that so slight differences in reported temperatures are normal.
For temperature testing, you can use Prime95 - Small FFTs for testing. It equally loads all cores of a CPU so the temperatures reported from various monitoring programs should be almost exactly the same. Most other testing programs do not equally load the cores like Small FFTs does.
What data do you not understand? Post a picture or a specific question.
The best monitoring program for a Surface Pro 3 is ThrottleStop. It has a lot more features to get the most out of these devices but is intended for advanced users. I wrote both of these programs so these downloads are 100% safe.
ThrottleStop 8.00
https://drive.google.com/open?id=0B0dpSo9k93jDTE1fcHNtbUMwdGc