I don't get it...
Either you transpose, or you use a capo (means, without changing the chords) in one purpose : change the key of a song when you feel it would be easier for your voice.
So you can use it with every song. I'll give ya an example : You like playing the chords progression C / F / G / Am but it feels like it's too "low-pitched" when your sing. Then use a capo 2 to sing it a lil bit higher.
No one can tell you if one particular song fits with your voice, you have to deal with it =). Everyone's different in that case.
Though I would like to share a few advices in that case :
- I would recommand to learn how to transpose, so you can better understand the different keys, be able to create songs.
- use the wonderful freeware GlabUke to transpose easily : it allows you to add a chord progression, then click on a simple button to transpose it 1/2 tone higher or lower. So easy. And you can learn new chords, or avoid using difficult ones ;-)
- beware of capos made of steel if you habe a high-value uke : this can sometimes do harm to the neck. I'd use an elastic capo (plus, way cheaper !) if I'd have to.
Personaly, songs in C/F/Am/G are often too high-pitched for my voice, and the chord progression in Bb/F/Gm/Eb a lil bit too low-pitched. So one of my soprano is tuned in D and I sing it easily on it. Without using a capo 2.
But that's personal . Hope this help, I don't know if this was very clear lol