Southcoast ukes has an interesting article on tunings and why a particular tuning is best suited for the sized instrument. I play linear baritones.
http://www.southcoastukes.com/004.htm Dirk states the baritone resonantes best in a Bb key.
It's thought the baritone was first designed for kids to learn the top four strings of a guitar with a smaller sized instrument, Bb was the key used by most musicians of the day hence the resonant factor. The G tuning was introduced for the learning of the top 4 strings of a guitar. (Favilla website)
For a flurocarbon (non wound) linear G tuning I use Ken's Living Waters String. I hear you on the low sound so I suggest trying a set of Southcoast ML-RW: Medium Gauge Linear Set w/ round wound and tuning it to Bb. The wear on the fingernail is more your technique than the wound string or it may be you're using a really cheap wound string.
For me, a C tuned bari sounds washed out. I tried the cuatros in C tuning and liked it but missed the high A for finger pickin so changed back. On my baritones, I use wound strings as too me, they seem to bring out the resonance better. I found non-wound to soft for the style of playing I do. If needed when playing with others who have a C tuned instrument, I just play my Bb bari. with a capo on the 2nd fret and I'm playing in the key of C.
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Finding the right string is a continuing journey. I have three sets of different string makers sitting on my desk waiting to be tried, just for the sake of finding the perfect string. So far my favorites are the Living Waters and Southcoast. For my G tuned wound string setup, I'm trying a set of the Diaddario Titanium 2's. Sounds good so far but am anxious to try a few others.
With the strings you have on now, just use a capo to up the sound and use the same shapes you're using. A chord shape is a chord shape, it's where the shape is played on the fretboard that determines the key.
