I am not sure you are fully understanding what you are asking. An ARM processor is what is used to power a smartphone or a low cost tablet (Ipad, Galaxy Note, Surface RT, etc).
None of these systems have the processing, memory or graphics power in order to play this game unless it is scaled WAY back. It would also have to be written to support the ARM chipset calls. Windows RT will not run everything that Windows will run (hence the RT). In addition to that you cannot simply install a program on an RT program as it currently would have to go through the marketplace with its restrictions.
As far as a Surface Pro. Yes it will run FFXIV although I would recommend it be in lower settings to prevent overheating. Since 2.0 uses less resources then 2.0 should run just fine on a Surface Pro.
Here are the specs between the 2 (These are night and day differences)
http://www.engadget.com/2012/06/18/m...rt-and-window/
The Surface RT is an ARM tablet (similar to Android, Ipad and others) It is not a gaming machine unless the game is written to run on ARM (not nearly as powerful as a laptop or desktop. This is why it is so cheap).
The Surface pro is basically an Ultra Book type setup with an I5 and an Intel HD 4000 (which is capable of running FFXIV).
Basically a small laptop with the keyboard detached and a full touch screen with a special pen design.
Due to lack of space inside the case I would not put the setting too high due to cooling worries.
I hope this helps.