Take a look at the GPO audition, it will give you a good overview of what can be found in GPO. Regarding articulations, GPO has not been programmed this way, I mean, as a collection of articulations to play with. For most of the instruments, you will find only one patch programmed in such a way that it can play a really wide range of colors. For example for clainets, you have:
- Bb clarinet solo
- Bb clarinet for ensemble 1
- Bb clarinet for ensemble 2
- Bb clarinet for ensemble 3
- Eb clarinet
If you\'d like to hear what can be done with the solo clarinet alone, without mixing stacc, ff, pp, blah, blah, articulations, listen to the Mozart\'s clarinet concerto demo, at Garritan\'s site. It\'s worth!
And for ensambles, you just play with ensemble 1, 2 and 3, as you would in a real orchestra. The results are fantastic, specially with the woodwind section (but this is only my oppinion).
More compromised instruments may have additional articulations, for example the flute. You have vib, no vib and flutter. But generally, the philosophy is as for the clarinet example.