You could send it to mobile, email or address? I don't think I ever seen this before. When I sent btc, it was always to a btc address.
You can also send to mobile numbers and email addresses, but that's only for sending the bitcoin to other Coinbase users. For any other wallet you use a BTC address.
So after I type in the btc address, then click continue, it will tell me exactly the btc fee that will be deducted and the btc that will be sent to my nano ledger right? So the fee will be an onchain fee and should be no more than a few dollars? Again i remember when I withdrew from binance a while back, the btc withdraw fee was a flat 0.005 btc.
Mate you can just test it out yourself and you'd immediately have the answer. I don't have Coinbase so I don't know how it exactly works. But it should be the same general process as any other exchange; or at least very close.
As for the fees, it should be only be one or a few dollars, but I don't know how Coinbase calculate's the fee so you just have to test it out yourself. As for Binance, they demand a flat fee, so the fees are going to be different.