Both, and with the very vague 'to' - the emotional version seems more probable. However, it's emotional meaning is different than in English.
If you mean that you watched a beautiful, sad movie - that's "wzruszyć", and the sentence will be "Wzruszyło mnie to". The same if your friends gave you a really well-thought present which made you almost cry, and similar contexts which are positive.
In Polish, if something "dotknęło cię", that actually means that it offended you a bit, made you sad. "Dotknęło mnie to" could be a next phrase after a sentence saying "He said that I've gotten a bit plump" or "The boss said that my work performance is not that great, although I think that I actually work really hard".
What is the "to" at the end? Is it the subject of the sentence?
(At first I translated this as "It has touched it to me", assuming that the first "it" (subject) was included in the verb form (3PSN).)
If the "to" is at the end is indeed the subject, is this construction common?
I assume its to stress the "it"? or what part of the sentence does it stress, if any?
Hmmm... good question. This is a sentence that is not easy to translate into English, at least in Duolingo settings, where by definition we'd prefer the translation to be grammatically close to the Polish sentence.
Technically speaking, "to" is the subject here, true. But a better rendition of what this sentence actually means would be something in the direction of "I was offended/hurt by it" ('it' is probably 'what you said or did'). So it kinda is the subject, kinda is an object... I don't know if I make any sense here. I'm no syntactician, I'm not able to explain everything ;) I can only say that "Dotknęło mnie to" feels most natural to me. "To mnie dotknęło" also sounds natural and seems to mean exactly the same, but I'd put it second. I'm sorry I can't explain 'why'.