If you've never made a withdrawal from your Coinbase account, I would transfer a very small amount (maybe 0.001 bitcoin, around $10) first to make sure that you do it properly and it arrives in your wallet properly. If it all looks good, then you can transfer out the rest of your funds. You don't want to lose everything because you made a silly mistake with your first withdrawal.

Yes. If the mempool is full (as it is just now, thanks to the recent price growth), then it is more expensive to send a transaction. If you wait until the mempool is empty, then it will only cost a cent or two to make a transaction.

Sat/vB stands for satoshi per virtual byte. It is the way we measure fees. You have to pay a set fee in satoshi for each byte of space your transaction takes up. If you use multiple inputs, or send to multiple different addresses at once, then your transaction will be larger in bytes. The amount you pay in satoshi for each byte can vary, and the appropriate amount to spend depends on how full the mempool is. If you need a simple estimator for you, then use this site - https://www.coinb.in/#fees - and just copy the value at the bottom of the blue box labeled "Sat/Byte".