Can you fit two fingers or three?
I can't imagine playing a G with my first three fingers as I use my free first finger (and my pinky on the high E) for all kinds of melodic work. The hammer-on to the bottom two fingered notes in a C chord (while still retaining the two G notes on each E string), is something I use all the time. When playing the G, sometimes I mute the A string, sometimes not, depending on the song.
As for an A, I do a "mini-barre" (I like this term!) on the D and G strings with my first finger and get the C# on B with my 2nd finger (E string open). Again, especially with finger picking stuff, this frees up the 3rd and 4th fingers to do all kinds of noodling around the chord. Even though I have small hands, this kind of position allows lots of room on the A and gives you a nice crisp break so that you can make sure the high E rings out and you never have to worry about it being muted.
As for an A, I do a "mini-barre" (I like this term!) on the D and G strings with my first finger and get the C# on B with my 2nd finger (E string open). Again, especially with finger picking stuff, this frees up the 3rd and 4th fingers to do all kinds of noodling around the chord. Even though I have small hands, this kind of position allows lots of room on the A and gives you a nice crisp break so that you can make sure the high E rings out and you never have to worry about it being muted.