Hi Seersha, you'll only find your true range by picking songs and singing along. When you can't sing it or your throat strains then clip on the capo and try 2nd or 4th fret. If those aren't close go up or down one till you can manage the song comfortably.
Couple of tips
1) As you sing in practice your voice will warm up and songs that first you found rough will sweeten and become easier to make shine.
2) When you play in front of people you get a bit more adrenalin and sometimes you can sing an whole semitone (1 fret) higher.
2) Even when you find your key it may worth transposing chords. I've just taken 'When You Say Nothing At All' out of G and into key of C. In both cases I was playing on 3rd fret so it as actually Bflat but somehow Eflat suits me and the melody more.
3) Watch out for little trills and peaks pro-singers often put into a song. You don't usually need to do these. The true melody of a song will reveal itself.
4) There are some songs that just don't match in with your range well. Born singers are lucky enough to have wide ranges where this isn't true and with use and practice all our vocal ranges widen.
5) Some songs just match in with particular styles of speaking and accents. If you stumble on a lyric it may just be because you wouldn't say it that way. Sometimes it's alright to change them, but..
6) Some lyrics can't be messed with, you have to learn to breath and pace them right and then the song and guitar chords become far clearer.
To come back to your main point I've noticed that major chords tend to be confident and happy but minor chords tend to be sad and reflective. Sounds obvious however alot of pop songs tend to use the trick of a happy message with a minor key or a mournful song in a major. This somehow balances out, suggesting a silver lining to every cloud.
The real basic division in songs is between 12 bar blues derived stuff (3 chords) which tend to make '-- shapes on the fretboard and Western European progressions which work round a h shape. I'm sure Jerome and NELA can explain better. Don't worry about those for the moment concentrate on clear singing and keeping guitar and vocal together...
'The sound of the city seems to disappear'
