The simple reality in relation to Classical guitar is that if you want decent tone, you need nails. Often the case is that the longer the nails the better the tone. However, as one’s nails get longer, it is harder to play things like arpeggios. Every player has to find the balance that they are happy with. John Williams manages to play with rather short nails (mind you he is a god), while Pepe Romero, Julian Bream, etc. play with rather long nails.Generally the i is the shortest, the m next, the a the longest of the hand nails, and the thumb longer still.
For me personally, I have changed back and forth. I have had rather long nails for a while now (on the strong urging of my present teacher). However, I have been working a lot on Villa Lobos’s Etude #1, and I find with a shorter a, I can play the piece much better. So it takes time (think years) of experimentation to figure out nails length.
That being said, I would STRONGLY discourage the use of artificial nail hardeners. As guitarists, we demand a type of dynamic strength from our nails that people who use them purely for ornamental uses do not. Our nails are as a violinists bow, they are the tool by which we mold our music. If you need to, rub an oil into your nails after you shower (olive is fine), and more often if you wish. This helps keep them healthy. As well (but don’t do this when people are around or they make kill you), tapping your nails softly on a hard surface helps to stimulate the nail bed, and can help to harden the nail overall without making it brittle.
And as to the shaping on your nails, it is another art altogether. Most guitarists these days ramp their nails in that they play with a straight wrist rather than the strongly turned wrist of Segovia’s day. For me, I have to ramp my i and m towards the right, and my a towards the left. It helps to have someone who knows look at your nails and you can have a better idea.
And if you aren’t a member already, go join Delcamp. They are a great community of classical players, and there is a whole sub-forum dedicated to nails.
delcamp.net/forum/en/index.php
We should definitely get together soon so I can show you a thing or two.
Noel