.I am a classical guitarist who also wants to play the lute and vihuela. I have developed a right hand technique where I play on the left hand side of the nail (looking from the back of the hand) for the classical guitar, and on the right hand side for lute and vihuela. The right hand side of the nail is chamfered so I get more flesh contact between finger and string. I also use a different wrist position for classical guitar and lute/vihuela. I use the same amount of thumb nail contact for all three instruments.
It would be interesting to hear from any other members who also play classical guitar and lute or vihuela and what they do about right hand position and nails