<My actual example is Spirit Edge, which translates into Jan and Sulis respectively. I want to use this to name one of my weapons, but don't know if it should be Jansulis, Jan'sulis, Jan Sulis, Janen Sulis or some other combination in order to be proper.>
Compound nouns tend to take different forms within any given language depending on their common use or familiarity.
To separate this list out a bit:
-Janen Sulis is the genititve case and shows "possession"(quick definition). So, that shows more like Spirit's Edge or Edge of Spirit.
-Jan'sulis - I don't recall apostrophes being used in this way anywhere in any of the Elven words available, so I would say it might be a bit strange.
Now, looking through the Elven dictionary, most of the compounds I found in Elven were directly merged words or something making the use of particle nouns which result in a new meaning separate from the original words in the compound, basically a sort of prefixes. Since neither of the two words you have chosen are one of these "particle nouns," If Spirit Edge was a common enough saying, I'd say your best bet for accuracy is Jansulis. However, Jan Sulis looks better aesthetically to me, and assuming it isn't a common phrase in Elven, should also be acceptable if not preferable. This would also have the added benefit of helping to avoid any sound changes that might occur in Elven compounds, but that's a type of text and linguistic nerdiness better left unspoken. :P
Just my opinion of course. There could be specific rules that don't match with the usual logic. So, I guess it wasn't much help. ㅋㅋ
