As you already know, you will not be able to make considerable profit with that specs. But for learning, that will be more than enough I guess.
When we talk about pool mining, I see no problem in doing what you plan to do. You wouldn't be a nuisance as part of a pool, because you will only contribute you hash rate when you'r online and nothing when you'r off.
As for OS, there I can't help you much. Personally I use Windows, but you don't want that so... I have hear that Linux is good for mining too, but I don't know the details.
I guess you already have some coin on your mind that you want to mine and a pool which you will be using. If you need more info just ask.
There is nothing more to do than to wish you best of luck in your search for knowledge.
PS It would be interesting to see your coin on the market.