1.If my harsate is 10p, is it better to use one worker*10p or 10 workers*1p?
Either is fine.
But if each 1Ph/s is from separate Rigs/AISCs, I'd recommend you to separate the workers to easily monitor each miner's performance.
2.During the mining process, if I suddenly go offline and then come online again, will the previously submitted shares and time consumed be useless?
Since you're solo, you'll only get a reward when you mined a block.
Previous submitted shares aren't taken in consideration to the reward which is usually based from the coin that you're mining,
the fees in the transaction in your block and the solo pool owner's dev fee.
But answers will be specific and accurate if you tell which coin are you mining, the solo pool or software that you're using, and your miners setup.
