You can connect to desktop the same way both from Android and Windows RT. There's official Remote Desktop app from Microsoft in Play store. And I don't think that it will be fast enough to work with Lightroom without any lags and other problems.
Windows RT is locked platform, without jailbreak you can use only ModernUI apps (+these few desktop ones that are included in OS), after jailbreaking a couple more that were recompiled to ARM archtecture.
If you like hacking your device, like in Windows Mobile times, it may be good for you. But if it's all about working through remote desktop - first try to use this on your Transformer.
There's no WinRT tablet with pen support, sorry. Also, if you're thinking about working remotely with magnetic pen - this will just not work. You need to buy something with x86, like Surface Pro and use your software directly on it.
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