Hello, I am not completely inexperienced at mining. I did mine BTC back in 2013 right before the difficulty went up too high. I would like to start mining ALT coins and so I have 3 important questions for you guys:

1: Which Alt coin do you recommend to mine with GPUs at the moment?
2: Depending on the first answer, which mining pool should I join?
3: Should I go with linux as my default mining OS?

Thank you in advance!
=)